如何在 valueChanges 订阅中执行 combineLatest 运算符

Question

showDateCriteria = combineLatest(this.myForm.controls['name'].valueChanges, this.myForm.controls['age'].valueChanges, (name, age) => ({name, age}))
.subscribe(val => !(val.name==null ||val.age==null ));

我已经用 combineLatest 运算符和 showDateCriteria

尝试了这段代码

<div *ngIf="{{showDateCriteria | async}}">Show This</div>

即使满足特定条件，我也无法显示 <div>

https://stackblitz.com/edit/angular-rs3d7a

Answer 1

如错误所述ERROR Error: InvalidPipeArgument: '[object Object]' for pipe 'AsyncPipe'。

您正在尝试异步传输订阅，这没有意义。

您应该通过管道传输流。

this.showDateCriteria =
    combineLatest(
        this.myForm.controls['name'].valueChanges,
        this.myForm.controls['age'].valueChanges, (name, age) => ({
            name,
            age
        }));
this.showDateCriteria.subscribe(val => !(val.name == null || val.age == null));

编辑：

你也应该startWith，否则combineLatest不会触发。此外，逻辑错误，你应该 return boolean true 当它们中的任何一个不为空时，就像这样：

this.showDateCriteria = combineLatest(
    this.myForm.controls['name'].valueChanges.pipe(startWith(null)),
    this.myForm.controls['age'].valueChanges.pipe(startWith(null)),
    (name, age) => {
        console.log(name);
        return name || age;
    });

https://stackblitz.com/edit/angular-g6vi6k?file=src%2Fapp%2Fapp.component.ts

如何在 valueChanges 订阅中执行 combineLatest 运算符

How to do combineLatest operator in valueChanges subscriptions

reactive-programming

angular

rxjs6