[英]How to block a subscription call in constructor until completed?
How may I block a constructor, to wait for an Http call to return data?如何阻止构造函数以等待 Http 调用返回数据?
constructor() {
this.initRestData().subscribe();
// wait for data to be read
this.nextStep();
}
The data retreived by the initRestData() call is needed by other services/components in the application.应用程序中的其他服务/组件需要通过 initRestData() 调用检索到的数据。 I only have to do this at startup.
我只需要在启动时执行此操作。 If there is a better way to handle this then Observable that would be ok too.
如果有更好的方法来处理这个问题,那么 Observable 也可以。
You could chain the calls either inside the subscribe
or in a do
-operator:您可以在
subscribe
或do
-operator 中链接调用:
constructor() {
this.initRestData()
.do(receivedData => this.nextStep(receivedData)})
.subscribe();
}
For the case that other services rely on this.nextStep()
as well, you should implement this as a stream as well:对于其他服务也依赖
this.nextStep()
,您也应该将其实现为流:
private initialData$ = new BehaviorSubject<any>(null);
constructor() {
this.initRestData()
.do(data => this.initialData$.next(data))
.switchMap(() => this.nextStep())
.subscribe();
}
nextStep(): Observable<any> {
return this.initialData$
.filter(data => data != null)
.take(1)
.map(data => {
// do the logic of "nextStep"
// and return the result
});
}
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