Proposal: Input as Observable #5689

Sorry, I'm not good at English.

@Input property values are provided by parent component. The changes come asynchronously.
And if Input property was changed in the child component (it has the property as own property) , its change detector never notice it.

Goal

• Parent's input data and child's input property should be synchronized.
• Developers should understand that input properties are changed asynchronously.

Proposal

@Component({ selector: "child" })
class Child {
  @Input("input") inputValue: Observable<T>;

  ngOnInit() {
    this.inputValue.map((value)=>...);
  }
}

@Component({
  template: `
  <child [input]="valueToChild"></child>
  `
})
class Parent {
  valueToChild: T;
}

Above code does not work. Currently, to receive input as Observable<T>, I must write it like below.

@Component({ selector: "child" })
class Child {
  @Input("input") inputValue: Observable<T>
}

@Component({
  template: `
  <child [input]="valueToChild"></child>
  `
})
class Parent {
  valueToChild: Observable<T> = new Observable<T>((observer)=>{
    ...
    observer.next(val);
  });
}

Example: http://plnkr.co/edit/BWziQygApOezTENdTVp1?p=preview

This works well, but it's not essential. Parent's input data is a simple data originally.

I think this proposal make us happy.

Thanks.