我创建了下一个组件:
export class MonthView {
currentMonth: Moment = moment();
currentMonth$: Observable<Moment>;
currentMonthObserver: Observer<Moment>;
decrement: Function;
increment: Function;
constructor() {
this.currentMonth$ = new Observable((observer: Observer<Moment>) => {
this.currentMonthObserver = observer;
}).share();
const decrementCounter$: Observable<Function> = Observable.create((observer) => {
this.decrement = () => {
observer.next();
};
});
const incrementCounter$: Observable<Function> = Observable.create((observer) => {
this.increment = () => {
observer.next();
};
});
Observable
.merge(
decrementCounter$.map(() => - 1),
incrementCounter$.map(() => + 1)
)
.startWith(0)
.scan((currentCount: number, value: number) => currentCount + value)
.subscribe((count: number) => {
this.currentMonthObserver.next(this.currentMonth.clone().add(count, 'M')); //this.currentMonthObserver is undefined
});
}
}
问题:我正在:Cannot read property 'next' of undefined
针对这一this.currentMonthObserver.next
行(请参阅发布的代码中的注释)。
注意:我已经按照此博客上的教程进行操作,并且对RxJS完全陌生:https ://coryrylan.com/blog/angular-2-observable-data-services
模板:
<month-board [current-month]="currentMonth$"></month-board>
<button (click)="decrement()">Prev</button>
<button (click)="increment()">Next</button>
此代码this.currentMonthObserver = observer;
在
this.currentMonth$ = new Observable((observer: Observer<Moment>) => {
this.currentMonthObserver = observer;
}).share();
只会在您订阅时执行this.currentMonth
。因此this.currentMonthObserver
是null
因为它尚未初始化。
constructor() {
this.currentMonth$=new Subject().startWith(0).share();
}
increment() {
this.currentMonth$.next(1);
}
decrement() {
this.currentMonth$.next(-1);
}
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