投稿時間:2021-04-27 21:46:30 RSSフィード2021-04-27 21:00 分まとめ(55件)

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IT	気になる、記になる…	｢M2｣チップ搭載Macの登場はまだ先か − 今年末〜来年初頭になる可能性が浮上	https://taisy0.com/2021/04/27/139764.html	jioriku	2021-04-27 11:45:15
IT	MOONGIFT	Yahoo!ニュースの元記事を探す - Yahoo!ニュースから元記事へジャンプするユーザスクリプト	http://feedproxy.google.com/~r/moongift/~3/SA7IIgxY5ZI/	Yahooニュースの元記事を探すYahooニュースから元記事へジャンプするユーザスクリプトYahooニュースでは各メディアから提供されたニュース記事が掲載されています。	2021-04-27 21:00:00
python	Pythonタグが付けられた新着投稿 - Qiita	LeetCodeWeekly238C: 1839. Longest Substring Of All Vowels in Order 区間操作 一定の文字出現する最大の単調増加文字列	https://qiita.com/recuraki/items/654bcc8eff91c95b54f0		2021-04-27 20:10:09
js	JavaScriptタグが付けられた新着投稿 - Qiita	JQueryで2回目イベントが発火しない	https://qiita.com/yamato1491038/items/4fd925cc17577302bf65	JQueryで回目イベントが発火しない困ったこと・クリックでイベント発火させたい・初回は動いたが追加された要素のクリックイベントが発火されない問題のコードbottonclickfunction処理内容ボタンを押すことでイベント発火させ、ボタンを追加する処理をしました。	2021-04-27 20:31:25
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	ScalaのSlickでメインデータに追加データを左結合する実装で追加データが無いケースの記述方法	https://teratail.com/questions/335462?rss=all	そのSQLを実行した後のDB内データをgroupByする必要があります。	2021-04-27 21:00:02
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	javascriptで、出題される問題と同じ文章をタイピングして「正解・不正解」を表示させたい。	https://teratail.com/questions/335461?rss=all	javascriptで、出題される問題と同じ文章をタイピングして「正解・不正解」を表示させたい。	2021-04-27 20:52:32
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	React: 親コンポーネントから子コンポーネントにデータを渡したい	https://teratail.com/questions/335460?rss=all	React親コンポーネントから子コンポーネントにデータを渡したいReactで親コンポーネントから子コンポーネントに値を渡したいのですが、なかなかうまくできません。	2021-04-27 20:39:08
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	【React】react-draggableのドラッグ時動く関数内でデフォルトの引数を使いつつ、任意の渡したい変数も渡せる書き方がわからない。	https://teratail.com/questions/335459?rss=all	【React】reactdraggableのドラッグ時動く関数内でデフォルトの引数を使いつつ、任意の渡したい変数も渡せる書き方がわからない。	2021-04-27 20:23:15
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	Nuxtでページの初回アクセス時にFetchやAsync Dataフックの結果が取得できない	https://teratail.com/questions/335458?rss=all	Nuxtでページの初回アクセス時にFetchやAsyncDataフックの結果が取得できないNuxtjsにてPageのコンポーネントでaxiosを使ってデータを取得しようとしています。	2021-04-27 20:18:35
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	FileNotFoundError: [Errno 2] No such file or directory: '2.png'	https://teratail.com/questions/335457?rss=all	error	2021-04-27 20:18:11
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	useContextでuseRefを使う方法	https://teratail.com/questions/335456?rss=all	useContextでuseRefを使う方法現在、WebSocket通信をReactの複数のコンポーネントで共有したいと思っています。	2021-04-27 20:15:12
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	C++ swapの計算量について	https://teratail.com/questions/335455?rss=all	cnbspswap	2021-04-27 20:10:10
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	JavaScriptを使用して　複数階層のタブメニューのコンテンツ表示	https://teratail.com/questions/335454?rss=all	JavaScriptを使用して複数階層のタブメニューのコンテンツ表示解決したいことクリックしたボタンに該当するコンテンツ内容を表示させたい。	2021-04-27 20:06:16
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	自作HTMLのWordPress化について	https://teratail.com/questions/335453?rss=all	class	2021-04-27 20:04:13
AWS	AWSタグが付けられた新着投稿 - Qiita	CIDR(Classless Inter-Domain Routing)について	https://qiita.com/mzmz__02/items/6fe022d36f3f9d9193ff	の場合、がネットワーク部での部分がホスト部になる。	2021-04-27 20:27:39
AWS	AWSタグが付けられた新着投稿 - Qiita	【コピペ】AWS Cloud9+Docker ComposeでLaravel環境を構築その肆	https://qiita.com/_bobtabo_/items/b3b1654938dea3a79192	【コピペ】AWSCloudDockerComposeでLaravel環境を構築その参ただ、プッシュする度にユーザー名とパスワードを入力するのが面倒くさいので、SSH接続にする。	2021-04-27 20:19:42
Git	Gitタグが付けられた新着投稿 - Qiita	[Git] 日付以降のコミットログだけを表示	https://qiita.com/kke1229/items/d0027688886d36fc494a	gitlogafter	2021-04-27 20:20:05
技術ブログ	Developers.IO	IAM ロールを 1000 個作って遊んでいたら AWS 利用費が 50 ドルを超えていた話を JAWS-UG 初心者支部で LT しました	https://dev.classmethod.jp/articles/jawsug_bgnr-36-shikujiri-iamrole-1000/	jawsug	2021-04-27 11:41:10
海外TECH	DEV Community	Sharpen your Ruby: Working with Numbers	https://dev.to/ericchapman/sharpen-your-ruby-working-with-numbers-3ki9	Sharpen your Ruby Working with NumbersI develop in Javascript Python PHP and Ruby By far Ruby is my favorite programming language Together let start a journey and revisit our Ruby foundations Each post will include some theory but also exercise and solution If you have any questions comments or your are new and need help you can comment below or send me a message Numbers Type in RubyIn Ruby the two numbers primary type are Integer and Float Integerage Floatprice Attention In Ruby manipulating integers always end up with an integernumber Why this division return Because both numbers are integer and Ruby assumed that you would want a rounded value so it rounded it to the nearest whole number which is in this case Ok but what can I get the right value with decimal Yes just use a float in the equationnumber Arithmetic Order of OperationsIf we try to run this code what will be the value In which order the operation will be run In Ruby the order of operation isParenthesesExponentMultiplicationDivisionAdditionSubtractionA old trick to remember this order is to take the first letter of each item that give the word PEMDASLet s do example result Here the order of operation to make that result possible Parentheses Exponent Multiplication Division Final Addition and Subtraction Numbers methodsHere are some numbers manipulation methods Roundnumber round Round downnumber floor Round upnumber ceil Next next Is number event puts even true Is number odd puts odd false Generate a random numberrandom number rand ExerciceCreate a little program that Generate a random number between and That will generate a float number Use the round method to round your random number Create an arithmetic operation using all the PEMDAS item and try figure out the result without looking at Ruby result Solutionnumber rand round Example onlynumber ConclusionThat s it for today The journey just started stay tune for the next post very soon later today or tomorrow If you have any comments or questions please do so here or send me a message on twitter I am new on twitter so if you want to make me happyFollow me Follow justericchapman	2021-04-27 11:46:32
海外TECH	DEV Community	Build a Word Guessing Game in Python	https://dev.to/thenerdydev/build-a-word-guessing-game-in-python-pij	Build a Word Guessing Game in PythonIn this video we will see how we can make a Word Guessing Game in Python The idea here is that user will be offered a pre defined number of chances and will be presented with a word that the user would have to guess The game ends when the user guesses the entire word completely or the number of chances to guess the entire word gets exhausted in which case the user looses Video Follow me on Twitter Make sure to subscribe to the channel and give a follow here for more such tutorials and videos	2021-04-27 11:44:19
海外TECH	DEV Community	useReducer instead of useState while calling APIs!	https://dev.to/ms_yogii/usereducer-instead-of-usestate-while-calling-apis-3e1l	useReducer instead of useState while calling APIs Hello folks It s been a while since React has introduced Hooks and we all fell in love with it s patterns and ease of use Though this is the case many of us do not leverage all the features hooks provide and useReducer is one of them Because useState is the hook which we learn first we do not make much use of useReducer hook So in this article I will be focussing on useReducer and will walk you through the best use cases to implement it So let s dive in What is useReducer useReducer is another hook used for the modern state management in React This concept was introduced in Redux first and then it is adapted by React as well Typically reducer is a function which accepts two arguments state and action Based on the action provided reducer will perform some operations on a state and returns a new updated state In context of React useReducer also performs similar state management You can read more about useReducer in detail in the react documentation How to use it for API calls You must have got the basic idea of useReducer hook till now Let s just dive straight into the code and understand how using useReducer will make our code more efficient over useState Let s first start with an API call using simple useState It will look something like this user component using useState const User gt const userDetails setUserdetails useState const loading setLoading useState false const error setError useState useEffect gt setLoading true const getUsers async gt let response await axios get users if response status setUserdetails response data setError false return setError response error getUsers setLoading false return lt div gt loading lt p gt loading lt p gt error lt p gt error lt p gt lt ul gt userDetails map user gt lt li key user id gt lt h gt user name lt h gt lt p gt user location lt p gt lt li gt lt ul gt lt div gt export default User This is a very basic API call In real life scenarios we have to manage more states than this But for starters let s assume we have states to manage and those are dependent on each other When our application gets more complex at times we end up defining more than states In such scenarios if we are using only useState then it becomes very tedious to keep track of all the states and to update them synchronously To solve all these problems a better approach is using useReducer Let s see the same API call using useReducer user component using useReducerconst ACTIONS CALL API call api SUCCESS success ERROR error const userDetailsReducer state action gt switch action type case ACTIONS CALL API return state loading true case ACTIONS SUCCESS return state loading false userDetails action data case ACTIONS ERROR return state loading false error action error const initialState userDetails loading false error null const User gt const state dispatch useReducer userDetailsReducer initialState const userDetails loading error state useEffect gt dispatch type ACTIONS CALL API const getUsers async gt let response await axios get users if response status dispatch type ACTIONS SUCCESS data response data return dispatch type ACTIONS SUCCESS error response error getUsers return lt div gt loading lt p gt loading lt p gt error lt p gt error lt p gt lt ul gt userDetails map user gt lt li key user id gt lt h gt user name lt h gt lt p gt user location lt p gt lt li gt lt ul gt lt div gt export default User Here we are using a dispatch function to call our reducer Inside the reducer the switch case is defined to handle the actions provided by the dispatch function The actions object declared above will make sure that every time we pass predefined action to the dispatch function You can skip that step and use strings directly Inside each switch case we are performing operations on the state given and returning a new state I know your first reaction seeing the code would be this looks lengthy But trust me it makes more sense The useReducer hook accepts two parameters a reducer function and initial state Reducer function will perform all the state updations on the state provided But what are the benefits of doing this State will update in a single function based on the action and it will be dependent on previous When we pass action to the reducer we tell it what operation to perform on a previous state This way we can make sure all the states are in sync with that operation and there is a very less chance of missing any updates on a state Easy to manage complex statesAs one function is updating states it is easier to manage complex states containing arrays and objects We can useReducer effectively to handle updates on objects and arrays Easy to test and predictableReducers are pure functions and perform operations based on predefined actions Hence they do not have any side effects and will return the same values when given the same arguments This makes them predictable and easy to test when implemented When to choose useReducer over useState useReducers are good to choose over useState but not every time If your use case is simple they will add unnecessary complexity to your code I use this couple of rules to choose useReducer over useState If there are many states dependent on each other If the state is a complex object I hope these rules will help you as well to decide which state management hook to go for If you have any other factor to choose between these two let me know in the comments Thank you for reading this article Hope it will help you in some way Keep learning	2021-04-27 11:04:28
海外TECH	DEV Community	Functional Reactive Programming in Angular with RxJS	https://dev.to/asayerio_techblog/functional-reactive-programming-in-angular-with-rxjs-5f1j	Functional Reactive Programming in Angular with RxJSby author Arek NawoAlongside React and Vue Angular is considered to be one of the top JS UI frameworks However it differentiates itself through a couple of factors Unlike the other top it s a full blown framework coming with everything you d want a framework to have It also has a unique architecture and ideology This can be seen in its primary language being TypeScript instead of JavaScript its heavy use of decorators and its noticeable influence of the Functional Reactive Programming paradigm and adoption of many of its patterns Functional Reactive ProgrammingFunctional Reactive Programming FRP focuses on the concept of streams and how they can be used to handle both synchronous and asynchronous data to build applications in a declarative manner It s a combination of Reactive Programming which focuses on over time change management and async data flows and Functional Programming which provides ways to control it In Angular FRP is used mostly through Observables These in turn make for an interface for handling async operations such as AJAX requests or user input events All of that and more is implemented with the RxJS library What is RxJS The RxJS Reactive Extensions for JavaScript library provides an implementation of Observables for JavaScript alongside other “satellite types and operators to work with them All these features make for a solid toolkit for dealing with async operations in a functional and reactive manner Overall it s the library to go to whenever you re dealing with FRP in JS and any other language supported by the ReactiveX project That s why Angular and many other projects choose it to be their observable implementation and form their foundation for a clean FRP codebase ObservablesTo properly understand RxJS and FRP in general we have to start with the concept of observables Behind every observable there s a stream that represents a sequence of values spread over time Examples of such sequences include simple arbitrary data user input events fetched data timeouts intervals etc Essentially everything async even more so if it repeats over time Observables play the role of functional wrappers around such streams They provide you a way to subscribe to and unsubscribe from the stream to listen for incoming values and APIs to transform the incoming data to your needs Creating observablesWhen creating an observable it s important to remember that at its core it s just a function binding an observer listening for changes to the producer sourcing values Take a look at how we can create a basic observable from an interval that will emit increasing values every s import Observable from rxjs const observable new Observable subscriber gt let count const interval setInterval gt subscriber next count count return gt clearInterval interval You can see that our observable is created with the Observable interface from RxJS Inside the function we access the subscriber and control the notification flow through the methods like next The returned callback is meant for disposing of the observable a perfect place to clear the running interval All that is assigned to a variable ending with not a requirement but a common naming convention for observables Creation functionsThe code is pretty clear already but why write so much if we can just use one of RxJS s creation functions to do it faster Check it out import interval from rxjs const observable interval Short and simple RxJS is full of such functions Let me show you some examples import from fromEvent of from rxjs import fromFetch from rxjs fetch from fetch example json from fromEvent document getElementById btn click of fromFetch example json Using the from function we can create an observable from an array like iterable observable or promise value of seems fairly similar though a bit different and more limited It ll also let you create observable from arbitrary values but this time each argument will become a separate item in the resulting sequence So of will result in an observable sequence of item while from will result in a sequence of Keep in mind that the same applies for Array like strings e g test vs t e s t fromEvent comes closer to the UI as it creates an observable from UI events Provide the target with an event name and you re good to go Last but not least fromFetch provides a shortcut for creating observable from fetch directly That s simpler and cleaner than using from fetch RxJS is full of functions like from of or fromFetch It provides you with multiple ways of doing the same thing where each one of them is good for different scenarios It s like Lodash for observables very helpful with tons of choice going around But if an observable is just a function binding producer with an observer then none of the observables we ve already created do anything We ve got the producer and wrapping observable but without the observer it s useless Let s see how we can fix this while learning about observers and subscriptions along the way SubscriptionsLet s come back to our simple interval example and see how we can subscribe to it to receive updates import interval from rxjs const observable interval const subscription observable subscribe value gt console log value As you can see subscribing to an observable is really easy Just pass your observer to the subscribe call and you re done The call will return a subscription object to represent the execution of the observable and control the subscription ObserversNow it s important to note that an observer is an object a set of callbacks rather than a singular function The above snippet represents a common shortcut to handle only one type of notification next instead of them all next error and complete callbacks as separate argumentsobservable subscribe value gt console log value error gt console error error gt console log complete orobservable subscribe next value console log value error error console error error complete console log complete None of the mentioned callbacks are required though you ll most certainly want at least one Also callback names next error and complete are equivalent to the methods you use to control notifications flow from the observable side In our custom interval observable we ve used only next but error and complete are also available alongside other methods UnsubscribeThe returned subscription object the result of a subscribe call is handy for controlling the subscription most importantly unsubscribing from it Having access to the subscription object we can unsubscribe through a simple unsubscribe call subscription unsubscribe Unsubscribing is important as it manages the proper execution of the observable and the dispose function calls to prevent memory leaks So whenever you re done using your subscription remember to call unsubscribe Multiple subscriptionsOne more thing related to subscriptions worth discussing is what happens when you subscribe to the same observable more than time const observable interval observable subscribe value gt console log Subscription A value setTimeout gt observable subscribe value gt console log Subscription B value Console output Subscription A Subscription A Subscription A Subscription B Subscription A Subscription B Notice that we ve got different values from both subscriptions even though we ve subscribed to the same observable Both of them have separate intervals which can be seen in the output especially with the added setTimeout call What you see is a result of our observable being cold let s discuss what it means Frontend MonitoringDebugging a web application in production may be challenging and time consuming Asayer is a frontend monitoring tool that replays everything your users do and shows how your app behaves for every issue It s like having your browser s inspector open while looking over your user s shoulder Asayer lets you reproduce issues aggregate JS errors and monitor your app s performance Asayer offers plugins for capturing the state of your Redux or VueX store and for inspecting Fetch requests and GraphQL queries Happy debugging for modern frontend teams Start monitoring your web app for free Hot or coldTo determine whether an observable is hot or cold we have to look at how it handles its producer Being the source of the observable s data the producer can be created either “inside or “outside the observable You can see this clearly in our example of creating the interval observable from scratch import Observable from rxjs const observable new Observable subscriber gt let count const interval setInterval gt subscriber next count count return gt clearInterval interval Here you can think of a producer as a combination of the interval and count variable It s clearly created inside our observable s “blueprint function making the observable cold This brings along several interesting properties A new producer is created for every subscription For a new subscription the same sequence of values will be returned Values start being emitted only after the first subscription as no producer exists before that Because of those properties cold observable are desirable for some scenarios and undesirable for others E g in the interval example above the cold approach is usually the one you ll want However when we re considering observables wrapping user input events or AJAX requests we ll be respectively forced to use hot observables or be very careful not to cause unnecessary requests with cold observables There s also a potential for memory leaks when we forget about unused running observable especially a cold one To better understand hot observables and their properties let s make some changes to our interval observable to make it hot import Observable from rxjs let count const intervalCallbacks setInterval gt intervalCallbacks forEach callback gt callback count count const observable new Observable subscriber gt const callback count gt subscriber next count intervalCallbacks push callback return gt intervalCallbacks splice intervalCallbacks indexOf callback With the new hot interval observable above all subscribers will receive the same values no matter when they subscribe However that s not all Hot observables also have some other properties There s a single existing producer to handle all subscriptionsThe producer generates values even if there s no subscriber Built in creation functionsKnowing the difference between cold and hot observables becomes even more important when considering different creation functions and other sources of observables beyond our direct control Generally most questionable observable sources should document whether they re hot or cold but if not then a rule of thumb would be Everything is cold unless it makes real sense to be otherwise And so all of the creation functions we ve covered but fromEvent are cold It makes sense as you wouldn t make user input events wait until you subscribe to the observable Another important thing to notice is in the fromFetch and other HTTP request related observables like those from Angular s HttpClient They re all cold and so even though you can manage your requests easily with them you still have to watch yourself as every subscription will result in another request There is a way to make cold observable hot and we ll cover it in a bit but first let s talk about how you can manage your subscriptions even better AsyncPipeWe ve already covered how you can subscribe to an observer and how you can manage the subscription with the unsubscribe method on the subscription object or e g complete inside the observable s “blueprint function However in Angular there s one more way to manage your subscriptions that you should know about and that s AsyncPipe It allows you to subscribe to an observable right from the Angular template More than that it ll automatically call unsubscribe when your component will be destroyed making subscription management and memory leak prevention that much easier It ll also automatically use the latest value from the stream update the view as needed and even resubscribe to a new observable if that s necessary As for the usage AsyncPipe has a simple form of async placed right after the observable or promise of choice In the following example we use it to access products observable s data loop through it and list the results Component template lt ul gt lt li ngFor let product of products async gt product name lt li gt lt ul gt export class AsyncObservablePipeComponent products Observable lt Product gt this productsService getProducts OperatorsSo we ve got the basics of observables pretty well covered We know how to create them subscribe unsubscribe from them and generally control the notification flow Now it s time to talk about operators the manipulation APIs which make the “Functional in FRP really shine Operators are the bread and butter of the RxJS library Whereas the Observable interface forms a solid foundation operators are how the magic happens They allow you to manipulate your collections through composable code in a declarative manner The fun fact is we ve already got to know some operators The so called “creation functions are really one of two types of operators the creation operators Now we ll be discovering the second type the pipable operators functions that you can pipe to observables to create new altered observables with desired behaviors Pipe methodThere are two ways to use the operator The first one is just to call it and pass an observer to it Given an operator named operator it would look like this const newObservable operator observable Notice the first pairs of rounded brackets It s used to construct configure the operator If any arguments are needed they ll go here If not the call stays for API consistency However given the composable nature of operators you can see how the above syntax could quickly become unreadable due to deep call nesting That s where the Observable s pipe method comes in It allows you to pipe multiple operators with clean readable syntax const newObservable observable pipe operator operatorA operatorB operatorC operatorD The pipe syntax is so preferable in fact that it s a recommended practice to use it even for single operators Common operatorsNow that we know how to pipe operators it s time to learn some of them RxJS provides so many operators that it s impossible to cover them all in a single blog post Instead we ll only cover some to give you an example Like arrays observables and underlying streams represent sequences of data just asynchronously That s why many operators share their use cases and naming with array methods So we ve got filter map every find reduce and many more As for some usage examples import of from rxjs import every filter find map reduce from rxjs operators const observable of Filter for multiples of const filteredObservable observable pipe filter value gt value Potential output Other examples Map to the power of observable pipe map value gt value value Is every number greater than observable pipe every value gt value gt false Find observable pipe find value gt value Sum all valuesobservable pipe reduce accumulator value gt accumulator value Cold observables output only when subscribed tofilteredObservable subscribe value gt console log value Notice how operators are imported from a separate module rxjs operators likely for the sake of organization as there are so many As for the operators themselves you can see that the way I ve used them heavily resembles the use of array methods especially with the numeric observable sequence However the magic of observables is that it doesn t have to be synchronous numeric data you re dealing with nor that you have to pipe only a single operator at a time You can mix and match and do all kinds of complex async or sync operations in a clean FRP manner Take a look at the following example where we process the output from async fetch request directly import fromFetch from rxjs fetch import concatAll filter map from rxjs operators const observable fromFetch example json selector response return response json pipe concatAll filter value gt value experience gt map value gt value name subscribe value gt console log value To fromFetch aside from the request URL we pass config object with selector callback for “unwrapping the fetched data Then presuming the JSON data is an array of objects describing users we process it with several operators First concatAll “splits the input array into separate sequence items to then be processed through filter and map All in a clean functional way Operators in UIApart from processing data observables and operators can also be useful in the UI especially when dealing with user input events Consider the following example where we use fromEvent creation function and filter operator to determine the number of clicks on an Angular button import AfterViewInit Component ElementRef EventEmitter Input Output ViewChild from angular core import fromEvent from rxjs import filter from rxjs operators Component selector btn template lt button btn gt Button lt button gt export class ButtonComponent implements AfterViewInit ViewChild btn static true el ElementRef lt HTMLButtonElement gt Output multiClick multiClick new EventEmitter lt MouseEvent gt Input requiredClicks requiredClicks number ngAfterViewInit fromEvent lt MouseEvent gt this el nativeElement click pipe filter value gt value detail this requiredClicks subscribe event gt this multiClick emit event We first use ElementRef and ViewChild decorator to gain access to the DOM button element Then in the ngAfterViewInit hook when the reference is ready we access it and start listening for click events with fromEvent By piping the observable through filter we check if the number of clicks under detail property matches the required number of clicks Lastly the resulting observable is subscribed to and emits events whenever necessary The code is functional simple and very readable Observers integrate well with Angular s components and overall structure As for an example usage of this component lt btn requiredClicks multiClick handleTripleClick event gt lt btn gt Converting hot observable to coldWhen discussing hot and cold observables I told you there s a way to convert a cold observable to a hot one That s possible thanks to some complex transformations which we can benefit from through a simple share operator import interval from rxjs import share from rxjs operators const observable interval pipe share observable subscribe value gt console log Subscription A value setTimeout gt observable subscribe value gt console log Subscription B value Console output Subscription A Subscription A Subscription A Subscription B Subscription A Subscription B The example from above is the same one we ve analyzed when discussing multiple subscriptions to one observable Notice the small difference piping of the share operator Thanks to this little change all our subscriptions will now get the same synchronized values no matter when they subscribe We ve just made a hot observable out of a cold one Error handlingWith the knowledge of operators we can now discuss how we should handle errors in observables We ve already got a glimpse of that with observers in subscribe method and their error callback However this way of handling errors has some big disadvantages First off it s finite meaning you can t easily recover from error even if you want to And also it goes against Angular s philosophy of separation of concerns There s a special operator that can be used for handling errors and solves both of these issues catchError To show its use let s bring up the fromFetch creation function import fromFetch from rxjs fetch import catchError retry from rxjs operators const observable fromFetch example json pipe retry catchError gt return Promise resolve We pipe both retry and catchError to our fromFetch observable retry is another useful operator that will resubscribe to the source observer upon error and retry running it up to the specified number of resubscriptions catchError gets handed a callback that upon receiving the caught error and source observable decides whether to throw this or new error return the source observable and try again or return any different kind of value In the example above I return Promise resolve as the “fallback value upon error This will in turn result in an empty array being retrieved on the subscription s end when a fetching error happens as fromFetch will automatically unwrap the promise This short overview should provide you with a basic notion of what catchError and other error handling operators are all about They might seem a bit unnecessary right here but in more complex scenarios with nested observables when used alongside AsyncPipe or in other edge cases they become invaluable SummaryThis detailed primer on RxJS and FRP in Angular should leave you with a solid understanding of the basics It s enough to start experimenting on your own or go to learn more advanced topics such as observable nesting Subjects Schedulers or complex operators RxJS and Angular form a great combo that can lead to simple clean and enjoyable code when used correctly Sure it requires learning a few new concepts but this knowledge then pays off in better code and a better understanding of it	2021-04-27 11:02:58
Apple	AppleInsider - Frontpage News	Apple's ad platform could benefit from privacy push	https://appleinsider.com/articles/21/04/27/apples-ad-platform-could-benefit-from-privacy-push?utm_medium=rss	Apple x s ad platform could benefit from privacy pushApple s introduction of App Tracking Transparency could be beneficial to its own advertising business with ad executives claiming clients could gain more data about ad performance for iOS devices than through third party platforms Apple s launch of App Tracking Transparency on Monday has the potential to limit the amount of data that marketing firms can generate from tracking the online activities of potential ad viewers While this could ultimately impact the amount of revenue generated by advertising it may also help make Apple s own advertising platform a more attractive proposition According to advertising executives and other observers speaking to the Wall Street Journal ATT could give Apple s advertising system an edge To ad agencies this edge could be an immediacy of data Read more	2021-04-27 11:51:48
Apple	AppleInsider - Frontpage News	EU to charge Apple over anti-competitive App Store fees this week	https://appleinsider.com/articles/21/04/27/eu-to-charge-apple-over-anti-competitive-app-store-fees-this-week?utm_medium=rss	EU to charge Apple over anti competitive App Store fees this weekThe European Union is expected to charge Apple over anticompetitive behavior allegations this week almost two years after Spotify lodged its complaint with the European Commission about the App Store and Apple Music In Spotify wrote to the European Commission about the App Store s percent commission for transactions Spotify believed it put the company at a disadvantage as Apple Music wasn t affected by the same charge Read more	2021-04-27 11:06:10
Apple	AppleInsider - Frontpage News	Apple's 'M2' processor enters mass production for MacBook Pro	https://appleinsider.com/articles/21/04/27/apples-m2-processor-enters-mass-production-for-macbook-pro?utm_medium=rss	Apple x s x M x processor enters mass production for MacBook ProThe second Apple Silicon processor has reportedly entered volume production and will first appear in MacBook Pro models from the second half of Apple s MacBook Pro is expected to be the first Mac to use the forthcoming M processorA new supply chain report is backing up previous claims that Apple has rescheduled new MacBook Pro manufacturing to the second half of Read more	2021-04-27 11:03:59
海外TECH	Engadget	The Morning After: Tesla's record car sales, despite COVID-19	https://www.engadget.com/the-morning-after-teslas-record-car-sales-despite-covid-19-113044429.html	The Morning After Tesla x s record car sales despite COVID Today s headlines Tesla built sold and shipped more vehicles in this last quarter than ever before Apple releases iOS with stricter app tracking privacy and Zoom s Immersive View crams up to people inside one virtual background	2021-04-27 11:30:44
海外TECH	Engadget	EU set to charge Apple over anti-competitive App Store policies this week	https://www.engadget.com/eu-apple-anti-competitive-app-store-policies-111753790.html	EU set to charge Apple over anti competitive App Store policies this weekThe EU will reportedly file anti competitive behaviour charges against Apple later this week over issues relating to its App Store policies	2021-04-27 11:17:53
海外TECH	Engadget	The final 'Resident Evil Village' demo will be playable for 8 days	https://www.engadget.com/resident-evil-village-demo-playable-8-days-110507712.html	daysre	2021-04-27 11:05:07
Cisco	Cisco Blog	MacStadium Makes a Leap Toward Data Center Automation with Cisco Nexus Dashboard	https://blogs.cisco.com/datacenter/macstadium-makes-a-leap-toward-data-center-automation-with-cisco-nexus-dashboard	MacStadium Makes a Leap Toward Data Center Automation with Cisco Nexus DashboardWith Cisco Nexus Dashboard MacStadium now has a singular management platform with the ability to automate and quickly scale its infrastructure to meet new customer demand without adding more specialists	2021-04-27 12:00:01
医療系	医療介護 CBnews	薬剤師過剰、45年に最大12万人超-厚労省推計	https://www.cbnews.jp/news/entry/20210427200001	厚生労働省	2021-04-27 20:35:00
医療系	医療介護 CBnews	認知症疾患医療センターと関係機関の連携強化-秋田県が介護保険事業支援・老人福祉計画を公表	https://www.cbnews.jp/news/entry/20210427194845	介護保険	2021-04-27 20:05:00
海外ニュース	Japan Times latest articles	On Myanmar crisis, ASEAN pushes boundaries of ‘noninterference’	https://www.japantimes.co.jp/news/2021/04/27/asia-pacific/politics-diplomacy-asia-pacific/myanmar-asean-limits/	On Myanmar crisis ASEAN pushes boundaries of noninterference The summit s concluding consensus statement stretch the bounds of ASEAN s longstanding principle of noninterference in members internal affairs	2021-04-27 21:38:18
海外ニュース	Japan Times latest articles	Suga faces prospect of joining long list of short-term leaders	https://www.japantimes.co.jp/news/2021/04/27/national/politics-diplomacy/suga-short-term-risk/	emergency	2021-04-27 20:19:43
海外ニュース	Japan Times latest articles	Amputee Blake Leeper won’t be allowed to race with running blades	https://www.japantimes.co.jp/sports/2021/04/27/more-sports/track-field/blake-leeper-prosthetic-blades-rejected/	Amputee Blake Leeper won t be allowed to race with running bladesWorld Athletics has rejected an application from American double amputee Blake Leeper to run on particular running specific prostheses RSPs preventing him from competing in the	2021-04-27 21:26:31
海外ニュース	Japan Times latest articles	Italian clubs who break away to be banned from domestic competitions	https://www.japantimes.co.jp/sports/2021/04/27/soccer/italy-breakaway-club-ban/	Italian clubs who break away to be banned from domestic competitionsThe Italian soccer federation FIGC said on Monday that clubs who join a breakaway league would be banned from all domestic competitions including the first division	2021-04-27 21:02:51
海外ニュース	Japan Times latest articles	WBO superfly champ Kazuto Ioka had positive doping test before fight	https://www.japantimes.co.jp/sports/2021/04/27/more-sports/boxing-2/kazuto-ioka-doping/	WBO superfly champ Kazuto Ioka had positive doping test before fightWBO world super flyweight champion Kazuto Ioka had tested positive for doping in December when he defended the title for the second time sources familiar	2021-04-27 20:19:54
海外ニュース	Japan Times latest articles	‘Ultra-rare’ LeBron rookie card sells for record-setting $5.2 million	https://www.japantimes.co.jp/sports/2021/04/27/basketball/nba/lebron-rookie-card-record/	Ultra rare LeBron rookie card sells for record setting millionAn ultra rare signed rookie card for four time NBA champion LeBron James sold for million on Monday breaking the record for the most expensive basketball	2021-04-27 20:13:16
ニュース	BBC News - Home	Cabinet meets as pressure builds on Boris Johnson amid leaks	https://www.bbc.co.uk/news/uk-politics-56897213	cabinet	2021-04-27 11:49:35
ニュース	BBC News - Home	Covid-19: Vaccine offered to 42-year-olds in England	https://www.bbc.co.uk/news/uk-56899901	covid	2021-04-27 11:52:40
ニュース	BBC News - Home	Nazanin Zaghari-Ratcliffe's daughter not yet told mum faces prison again	https://www.bbc.co.uk/news/uk-56900912	husband	2021-04-27 11:27:12
ニュース	BBC News - Home	Meth lab found in raid near Redditch	https://www.bbc.co.uk/news/uk-england-coventry-warwickshire-56901616	chemicals	2021-04-27 11:43:26
LifeHuck	ライフハッカー［日本版］	マルチタスクが快適に｜ノートPCに合体させるモバイル液晶画面	https://www.lifehacker.jp/2021/04/233427gizmodo-sanwa-direct-mobile-display-for-laptops.html	紹介	2021-04-27 21:00:00
GCP	Google Cloud Platform Japan 公式ブログ	Google Cloud は公平なワクチン接種をどのように実現しているか	https://cloud.google.com/blog/ja/topics/public-sector/how-google-cloud-enabling-vaccine-equity/	これは米国の他の州が行ったことのない大がかりな事業であり、申し込みやスケジュール設定で障害が起きないように管理していました。	2021-04-27 12:00:00
北海道	北海道新聞	海洋放出撤回求める意見書　福島・南相馬市議会が可決	https://www.hokkaido-np.co.jp/article/538157/	南相馬市議会	2021-04-27 20:18:06
北海道	北海道新聞	台湾、中国出身監督のアカデミー受賞１面で　「アジア女性で初」	https://www.hokkaido-np.co.jp/article/538156/	米アカデミー賞	2021-04-27 20:15:52
北海道	北海道新聞	沖縄でプレジャーボート爆発、５人けが　事故調査官を派遣	https://www.hokkaido-np.co.jp/article/538168/	沖縄県本部	2021-04-27 20:14:59
北海道	北海道新聞	上司のアウティングで労災申請　東京の２０代男性、精神疾患に	https://www.hokkaido-np.co.jp/article/538164/	性的指向	2021-04-27 20:13:56
北海道	北海道新聞	コロナ変異株、釧根で初確認　釧路管内の４０代男性感染	https://www.hokkaido-np.co.jp/article/538127/	新型コロナウイルス	2021-04-27 20:09:42
北海道	北海道新聞	丸川五輪相、医療提供で都に苦言　小池氏は「実務的に詰め」	https://www.hokkaido-np.co.jp/article/538171/	記者会見	2021-04-27 20:08:00
北海道	北海道新聞	チューリップフェア２年ぶり　木古内・サラキ岬で１～５日　今年は球根販売のみ	https://www.hokkaido-np.co.jp/article/538170/	軍艦	2021-04-27 20:07:00
北海道	北海道新聞	凍結中の自動車道・陸別―足寄間事業、本年度中に再開へ	https://www.hokkaido-np.co.jp/article/538167/	北海道横断自動車道	2021-04-27 20:06:32
ニュース	Newsweek	気候変動の影響で地球の自転軸がずれた──最新研究	https://www.newsweekjapan.jp/stories/world/2021/04/post-96180.php	「この新たな所見は、地理極の移動と気候変動が過去に密接に関係していたことを示している」研究チームは、気候変動は地理極の方向が変わった唯一の理由ではないが、観測を行った期間については、気候変動が大きな影響を及ぼしたことは確かだと述べた。	2021-04-27 20:45:18
ニュース	Newsweek	ワクチン接種後でも、新型コロナ変異株が感染する「ブレイクスルー感染」が確認される	https://www.newsweekjapan.jp/stories/world/2021/04/post-96179.php	ワクチン接種後でも、新型コロナ変異株が感染する「ブレイクスルー感染」が確認される米ニューヨーク州で新型コロナウイルスワクチンを回接種して週間以上経過した名のうち、歳の女性と歳の女性の計名が新型コロナウイルスに感染した。	2021-04-27 20:00:54
IT	週刊アスキー	ソラコム、機能アップしたIoTダッシュボード「SORACOM Lagoon」提供開始	https://weekly.ascii.jp/elem/000/004/053/4053149/	soracom	2021-04-27 20:30:00
GCP	Cloud Blog JA	Google Cloud は公平なワクチン接種をどのように実現しているか	https://cloud.google.com/blog/ja/topics/public-sector/how-google-cloud-enabling-vaccine-equity/	これは米国の他の州が行ったことのない大がかりな事業であり、申し込みやスケジュール設定で障害が起きないように管理していました。	2021-04-27 12:00:00