函数返回后 Observable.forkJoin 调用延迟

Question

在组件中，我们订阅了来自服务的两个 http 返回结果，并且在服务中，两个 http 调用返回了可观察的。

在组件打字稿中

catalogPromise = this.ondemandService.getVodCatalog().subscribe((data) => {
        console.log(data);

        });

服务中：-

    getVodCatalog(url,user){
    return this.getVodCategories().map((data) => {
            let result,result2;
            let Observers = [],
            cats = [],
            catalogs = [];

            result=data.json();
            result.categorylist.forEach((catergory) => {
                cats.push(catergory.name);
                Observers.push(this.getCategoriesCatolog(catergory.id,{}));
            });
            console.log(Observers);
            Observable.forkJoin(Observers).subscribe((vodCatalogs)=> {
                vodCatalogs.forEach((vodeCatalog,idx)=>{
                    let v1 = vodeCatalog.json();
                    if(v1.vodlist)
                    {
                        catalogs.push({
                            label: cats[idx],
                            list: v1.vodlist
                            });
                    }
                });
                return catalogs;
            });

        })
    .catch(this.handleError);
}


    getVodCategories(){
        let url="http://CategoryList";
        let headers = new Headers({ 'Content-Type':     'application/json','Accept':'application/json, text/plain, */*'});
        let body = {
                offset: 0,
                count: -1,
                type: 'dfasd',
                categoryid: -1,
             };
        let options = new RequestOptions({
             headers: headers,
             url:url,
             withCredentials: true,
             timeout:30000,
             body:body
         });
         return this._http.post(url,body,options);
     }

     getCategoriesCatolog(cateogoryId,options){
         var url="http://VodList";
         let headers = new Headers({ 'Content-Type':    'application/json','Accept':'application/json, text/plain, */*' });
         let body = {
                  count: 100,
                  offset: 0,
                  orderType: 0,
                  categoryid: cateogoryId,
            };
            options = new RequestOptions({
             url:url,
             withCredentials: true,
             timeout:30000,
             body:body
         });
        return this._http.post(url,body,options);
    }

在服务中，getVodCategories() 和 getCategoriesCatolog() 返回 observable 结果，但是当我们尝试在组件中订阅它时，整个数据未定义，之后 Observable.forkjoin() 正在运行。

Answer 1

尽量避免嵌套的 observable ，像下面这样使用 merge insteda

Rx.Observable.merge(
  myService.upload('upload1'),
  myService.upload('upload2')
.take(2)
.subscribe({complete: () => { ... });