Angular 6 - rxjs 管道不适用于 valueChanges [英] Angular 6 - rxjs pipe not working on valueChanges

问题描述

我有一个带有文本输入的反应式表单.为了便于在我的打字稿中访问，我声明:

I have a reactive form, with a text input. For ease of access in my typescript, I declared:

get parentId(): FormControl {
    return this.addForm.get("parentId") as FormControl;
}

这部分工作正常，控件访问正常.

This part works, the control is properly accessed.

现在在我的 ngOnInit 中，如果我这样做:

Now in my ngOnInit if I do this:

this.parentId.valueChanges.subscribe(() => console.log("Changed"));

控制台日志按预期在输入中的每个字符更改时执行.但如果我这样做:

The console log is executed at every character changed in the input, as expected. But if I do this:

this.parentId.valueChanges.pipe(tap(() => console.log("Changed")));

什么都没发生.没有错误，没有任何东西.我也尝试过使用 map、switchMap 等.没有任何效果.管道似乎不适用于 valueChanges.我在我的代码中的其他地方对不同的 observable 使用了 pipe 方法，没有任何问题.

Nothing happens. No errors, no anything. I tried also using map, switchMap, etc.nothing works. It seems that the pipe does not work on valueChanges. I am using the pipe method elsewhere in my code on different observables without any problem.

我需要在这里使用管道来去抖动、贴图等

And I need to use pipe here in order to debounce, map, etc.

知道我做错了什么吗?

-- 编辑 --

这是来自 Angular Material 站点的代码示例，关于自动完成组件:

This is the code example from Angular Material site, on Autocomplete component:

ngOnInit() {
   this.filteredOptions = this.myControl.valueChanges
       .pipe(
          startWith(''),
          map(val => this.filter(val))
       );
}

最后没有订阅，示例有效.

There is no subscribe at the end and the example works.

推荐答案

您需要订阅才能激活Observable，

ngOnInit() {
   this.filteredOptions = this.myControl.valueChanges
       .pipe(
          startWith(''),
          map(val => this.filter(val))
       ).subscribe();
}

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