[英]Using shareReplay(1) in Angular - still invokes http request?
I've created a demo ( ng-run ) where I have a button which invokes an Http request.我创建了一个演示( ng-run ),其中有一个调用 Http 请求的按钮。
When the button is clicked, I invoke this method :单击按钮时,我调用此方法:
public getData(){
this._jokeService.getData().subscribe();
}
Which in turn invokes this ( from a service) :反过来调用这个(从服务):
public getData() {
return this.http.get(API_ENDPOINT).pipe(shareReplay(1))
}
The problem is that on every click - I still see a new http request initiated :问题是在每次点击时 - 我仍然看到一个新的 http 请求被启动:
Question:题:
Why doesn't shareReplay keeps the last value of the response?为什么 shareReplay 不保留响应的最后一个值?
How can I make my code to invoke the http only once and keep that value for future subscriptions ?如何让我的代码只调用一次 http 并保留该值以供将来订阅?
Edit: solution is here编辑: 解决方案在这里
If you call every time this.http.get(API_ENDPOINT).pipe(shareReplay(1))
, each time http request will be triggered.如果你每次都调用
this.http.get(API_ENDPOINT).pipe(shareReplay(1))
,每次 http 请求都会被触发。 If you want to make http call once and cache data, the following is recommended.如果要进行一次http调用并缓存数据,建议使用以下方法。
You first get the observable for data:您首先获得数据的 observable:
ngOninit(){
this.data$ = this._jokeService.getData().pipe(shareReplay(1));
}
Now subscribe multiple times:现在订阅多次:
public getData(){
this.data$.subscribe();
}
Your service:您的服务:
public getData() {
return this.http.get(API_ENDPOINT)
}
In service:在役:
getData$ = this.http.get(API_ENDPOINT).pipe(shareReplay(1));
In component, need to unsubscribe and you can subscribe multiple times with single API call:在组件中,需要取消订阅,您可以通过单个 API 调用多次订阅:
ngOninit(){
this.data$ = this._jokeService.getData$;
this.data$.subscribe()
}
In template, use:在模板中,使用:
*ngIf="data$ | async as data"
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