Question

我有一个带有以下代码的函数：

private foo() {
    let obs: Observable<any> = this._http.get<number>('/foo')

    obs.subscribe(x=> {
        console.log("foo : " + x)
    });

     this.blah(obs)
}

private blah(obs: Observable<any>) {
    obs.subscribe(x => {
       console.log("blah : " + x)
    })
}

此代码确实同时打印了foo和blah，同时它也会对我{http} /foo进行两次调用

我希望它只发生一次。我尝试在blah函数中替换subscribe do，但它不起作用。这里的问题是什么？

Answer 1

That's correct behavior. You're creating two subscriptions and since the http.get creates a "cold" Observable it makes two HTTP calls.

The easiest way to avoid this is to share the source Observable with the share() operator.

let obs = this._http.get<number>('/foo').share();

You could also create a ConnectableObservable with the publish() operator and connect to the shared source manually.

let obs = this._http.get<number>('/foo').publish();

obs.subscribe(x=> {
    console.log("foo : " + x)
});

this.blah(obs);

obs.connect();

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