多次订阅可观察的rxjs

时间:2016-11-29 10:18:30

标签: javascript rxjs observable subscription

我正在努力实现以下目标:

我有一个可以多次订阅的Observable,虽然我只想做一次处理。

export class DataLoader
{
    private loaded = false;
    private data: Data;
    private observable = null;

    load(): Observable<Data> {
        if(this.loaded) {
            console.log('Already loaded');
            return Observable.create((obs) => {
                obs.next(this.data);
                obs.complete();
            })
        }

        if(this.observable === null) {
            console.log('Creating observable');
            this.observable = Observable.create((obs) => {

                console.log('firing xhr');
                let xhr;

                xhr.onload = () => {
                    this.data = data;
                    this.loaded = true;
                    obs.next(data);
                    obs.complete();
                    this.observable = null;
                }

                xhr.onerror = () => {
                    obs.error(error);
                    this.observable = null;
                }
            });
        }

        return this.observable;
    }
}

假设我在两个不同的地方使用这个DataLoader,'xhr'只会执行一次。

...
Dataloader.load().subscribe();
...
#At another point in the code
Dataloader.load().subscribe();
...

控制台:

Creating observable
firing xhr
Already Loaded

只要请求不会在彼此之后过快地触发,这就可以正常工作。

为了演示,让我们把它放在for循环中:

for(let i = 0; i<10; i++) {
    DataLoader.load().subscribe();
}

在这种情况下,控制台如下所示:

Creating observable
firing xhr
firing xhr
firing xhr
firing xhr
firing xhr
firing xhr
firing xhr
firing xhr
firing xhr
firing xhr

我怎样才能在for循环中设法使用它? 我一直在研究一个主题/行为主题,但我似乎无法使其发挥作用。

cookies for buts

2 个答案:

答案 0 :(得分:0)

我使用以下方法解决了这个问题:

if(this.observable === null) {
    console.log('Creating observable');
    let source = Observable.create((obs) => {

        console.log('firing xhr');
        let xhr;

        xhr.onload = () => {
            this.data = data;
            this.loaded = true;
            obs.next(data);
            obs.complete();
            this.observable = null;
        }

        xhr.onerror = () => {
            obs.error(error);
            this.observable = null;
        }
    });

    let subject = new Subject();

    this.observable = source.multicast(subject);

    this.observable.connect();
}

http://reactivex.io/rxjs/manual/overview.html#multicasted-observables

答案 1 :(得分:0)

我选择使用简单的Promise,因为我只需要一个多播事件,但是rxjs似乎已经用"Subjects"处理了它

  return this.service.add(this.formModel.value, this.imageFile)
    .toPromise() // this.subscribe((x) => value = x, (err) => reject(err), () => resolve(value));
    .then(id => this.formVm.editMode(id));