angular 4 个顺序异步 http 请求，错误响应时取消

Question

我正在尝试制作 3 个顺序和异步（none 并行），使用 HttpClient 和 Observable.forkJoin.

到目前为止是这样的，首先是 fileOperations 数组：

requestPayloadObjects:any[];//array of objects sent to the same request 

//... after the array was built
this.requestPayloadObjects.forEach( ( payloadObject:any,i:number )=> {
   //_uploadApi.postDoc returns an http observable
   fileOperations.push( this._uploadApi.postDoc( payloadObject ) );
});

然后在我有一个可观察数组之后，我使用 Observable.forkJoin

// parallel subscriptions, all 3 observables are subscribed to asyncly
Observable.forkJoin(fileOperations).subscribe((res:any)=> {
        // If all http calls succeeded you get here
    },(err:any)=> {
        // If 1 of all 3 that were sent failed you get here
    });

然而我想要的是：

// NONE-parallel subscription  
Observable.forkJoin(fileOperations).subscribe((res:any)=> {
        // If all http calls succeeded you get here
    },(err:any)=> {
        // If 1 failed, you get here, but you do not send the others
    });

我确定 Observable.forkJoin 不是实现此目的的 Observable 方法，但什么是？如何进行 none 并行订阅，只有前一个订阅成功才能继续下一个订阅？使用 Observables 执行此操作的正确方法是什么？

Answer 1

我想 concatAll 就是您要找的。查看 rxjs documentation。

Answer 2

按照@MichaelKie 的建议使用Observable.concat，我设法通过以下方式解决了这个问题。

let requestPayloadObjects:any[] = [{...},{...},{...}];
let firstServerCall:Observable<any>; 

this.requestPayloadObjects.forEach( ( payloadObject:any,i:number )=> {
        let observable = this._uploadApi.postDoc(payloadObject:any);
        if(i===0) {
            firstServerCall = observable ;
        }
        else {
            firstServerCall = firstServerCall.concat(observable );
        };
});
firstServerCall.subscribe((res:any)=> {
  // 1. will get here after every successful response
  // 2. will continue on to send next http call after this
},(err:any)=> {
  // will get here if subscription fails, without continuing to the next observable.
})

angular 4 个顺序异步 http 请求，错误响应时取消

angular 4 sequential async http requests with cancellation on error response

angular

angular5

angular6

angular2-observables

angular-httpclient