无法在 ngOnDestroy() Angular 5 中取消订阅

Question

我无法取消订阅我的测试。 还有人有这个问题吗？？ （我做错什么了吗？）

基本测试：

describe('ngOnDestroy()', () => {
  it('should unsubscribe if isLoggedInSub is defined', async(() => {
    comp.ngOnInit();
    fixture.detectChanges();
    comp.ngOnDestroy();
    fixture.detectChanges();
    expect(comp.isLoggedInSub).not.toBeDefined();
  }));
});

控制台错误：

Uncaught Expected Subscriber({ closed: true, _parent: null, _parents: null, _subscriptions: null, syncErrorValue: null, syncErrorThrown: false, syncErrorThrowable: false, isStopped: true, destination: SafeSubscriber({ closed: false, _parent: null, _parents: null, _subscriptions: null, syncErrorValue: null, syncErrorThrown: false, syncErrorThrowable: false, isStopped: false, destination: Object({ closed: true, next: Function, error: Function, complete: Function }), _parentSubscriber: <circular reference: Object>, _context: <circular reference: Object>, _next: Function, _error: undefined, _complete: undefined }) }) not to be defined.
at Object.testing_3.async

Answer 1

如果您有一个主题并且您直接尝试以上述任何方法取消订阅，那么我们将面临此类错误。 示例：

//AppComponent.ts

export class AppComponent implements OnDestroy{
 appSubject:new Subject();
 appSubject.subscribe(()=>...)
 ngOnDestroy() {
   appSubject.unsubscribe(); // If your subject is passing the next value from a 
                         different component
 }
}

这通常会导致此错误，因为另一个组件引用了主题。

更好的方法是

export class AppComponent implements OnDestroy{
 appSubject:new Subject();
 $subjectSubscription:Subscription = appSubject.subscribe(()=>...)
 ngOnDestroy() {
   $subjectSubscription.unsubscribe();
 }
}