我使用Observables来携带从父组件到子组件的值。
这是我的顶级应用程序组件:
import { Component } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import { Observer } from 'rxjs/Observer';
import { ViewModel } from './ViewModel.data';
import { ViewComponent } from './ViewComponent.component';
@Component({
selector: ...,
directives: [
ROUTER_DIRECTIVES,
ViewComponent
],
precompile: [],
styles: [],
template: `
<div>
<ul class="nav nav-tabs">
<li *ngFor="let v of views"><a (click)="setView(v)">{{ v.name }}</a></li>
</ul>
<viewcomponent
*ngFor="let v of views"
[viewName]="v.name"
[activeViewObservable]="activeViewObservable"></viewcomponent>
</div>
`
})
export class AppComponent{
views:ViewModel[];
activeViewObservable:Observable<ViewModel>;
viewObserver:Observer<ViewModel>;
activeView:ViewModel;
constructor() {
this.views = [{name: 'one'}, {name: 'two'}, {name: 'three'}, {name: 'four'}];
this.activeViewObservable = new Observable<ViewModel>(observer => this.viewObserver = observer);
}
public setView(view:ViewModel):void {
this.viewObserver.next(view); // load values here
}
}
我在这里使用名为viewcomponent
的组件:
@Component({
selector: 'viewcomponent',
directives: [
ROUTER_DIRECTIVES
],
template: `
<div class="tab-pane" [ngClass]="{ 'active': isActive() }">
...
</div>
`
})
export class ViewComponent {
// these values are always the last view. why???
@Input() viewName:string;
@Input() activeViewObservable:Observable<TabViewModel>;
private activeView:ViewModel;
constructor() {}
ngOnInit() {
this.activeViewObservable.subscribe( //listen to values loaded with the viewObserver
activeView => {this.activeView = activeView;},
error => console.error(error));
}
public isActive():boolean {
let bool:boolean = false;
if (this.activeView) {
console.log(this.viewName); // <---- this value is always the last view, 'four'
bool = this.activeView.name == this.viewName;
}
console.log(bool);
return bool;
}
}
我正在使用的数据模型在这里:
export interface ViewModel {
name: string;
}
我正在尝试使用AppComponent
中的值加载观察者,然后在子项中订阅它们。但是,observable发出的值始终是最后一个元素。
我想调用父项中的setView
方法,然后将一个类应用于该特定的子视图。
答案 0 :(得分:1)
可能的解决方案如果您要在Subject
的实例化之外的.next()
上调用Observer
,请使用Observable
。 Subject
表现为两者。您可以将活动传递给它的地方单独订阅。 Plunker Example
为什么您的代码不起作用?
使用rxjs的代码可以这样写:
let viewObserver;
const myObservable = new Observable(observer => {
viewObserver = observer;
});
myObservable.subscribe(
activeView => {
console.log(1, activeView);
},
error => console.error(error));
myObservable.subscribe(
activeView => {
console.log(2, activeView);
},
error => console.error(error));
viewObserver.next({ name: 'one' });
https://jsfiddle.net/t5z9jyf0/
预期产量是多少?
2, { name: 'one' }
<强>为什么吗
让我们打开rxjs文档
关键点有:
使用Observer调用observable.subscribe时,该函数 订阅Observable.create(函数subscribe(observer){...})是 为那个给定的Observer运行。每次调用observable.subscribe 为给定的观察者触发它自己的独立设置。
let viewObserver;
var myObservable = new Observable<ViewModel>(function subscribe(observer) {
console.log(observer, observer.destination._next);
viewObserver = observer;
});
myObservable.subscribe( // this triggers subscribe function above
activeView => {
console.log(1, activeView);
},
error => console.error(error));
myObservable.subscribe( // this also triggers subscribe function above
activeView => {
console.log(2, activeView);
},
error => console.error(error));
viewObserver.next({ name: 'one' }); // notify subscriptions
https://jsfiddle.net/t5z9jyf0/1/
因此在
之后代码不起作用myObservable.subscribe(
activeView => {
console.log(2, activeView);
},
error => console.error(error));
方法已执行,viewObserver
将被覆盖,Subscriber
对象来自activeView => { console.log(2, activeView); }
,因此viewObserver.next
会给我们
console.log(2, { name: 'one' });
这就是为什么只执行最后一次订阅