Angular2用诺言获取路线的参数 [英] Angular2 Getting route's params with promises

问题描述

嘿，我已经尝试了以下代码:

Hey I have tried that following bit of code :

constructor(private _route: ActivatedRoute) {}

ngOnInit() {
  this._route.params.toPromise().then(data => {
     ...
  })
}

但是它什么也没做.如果我将toPromise().then替换为subscribe，则效果很好.知道为什么它行不通吗?我在项目的许多其他地方都使用过toPromise().then，效果很好.

However it doesn't do anyhting. If I swap toPromise().then by subscribe it works fine. Any idea why it wouldn't work ? I have used toPromise().then in many other places in my project and it works just fine.

推荐答案

_route.params发出多个事件.当路由更改仅更改路由的参数值时，路由器不会重新创建组件，而是仅发出另一个params值.

_route.params emits more than one event. When a route change only changes the parameter value of a route then the component is not re-created by the router but instead just another params value emitted.

因此，使用toPromise()可能不是一个好主意，但是有可能，例如使用first()，以便可观察对象在第一个事件之后完成，因此，toPromise()返回的承诺也将完成.

Therefore using toPromise() is probably not a good idea but it's possible, for example using first() so that the observable completes after the first event and therefore also the promise returned by toPromise() completes.

如果没有.first()，则当您离开路线(未验证)时，诺言便会完成.

Without .first() the promise completes when you navigate away from the route (not verified).

constructor(private _route: ActivatedRoute) {}

ngOnInit() {
  this._route.params.first().toPromise().then(data => {
     ...
  })
}

first需要导入.在较新的RxJs版本中，first需要像这样pipe(first())

first needs to be imported. In newer RxJs version first needs to be wrapped in pipe like this pipe(first())

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