Question

在每个循环中我都有一个嵌套的订阅，其中内部订阅将外部订阅的结果作为输入。我需要代码像在for循环中进行迭代时一样，它应该调用外部订阅并将其结果/输出传递给内部订阅。在这里，for循环应等到过程完成后再进行下一次迭代。在这里，我为此提供了一个演示

this.forVar.forEach(item =>{
   this.service.outerSubscribe(item).subscribe(res=>{
      //some coding here 
      this.service.innerSubscribe(res).subscribe(res1=>{//some coding here});
   });
//for each should iterate only after both subscribes are executed.  
});

Answer 1

尝试使用功能combineLatest和higher-order mapping operator之类的switchMap。

// use switchMap to get values from the inner subscription
const createNestedSubscriptionFromItem = item => 
  this.service.outerSubscribe(item).pipe(
    switchMap(res => this.service.innerSubscribe(res))
  );

// create an array of subscriptions
const subscriptions = this.forVar.map(item => 
  createNestedSubscriptionFromItem(item)
);

// use combineLatest to get updates from all results.
// here you can use other functions like merge or jorkJoin instead combineLatest. 
const allResults$ = combineLatest(subscriptions);

在官方API Reference中查看有关静态函数和运算符的更多信息；

仅在角度6中执行订阅方法的主体（嵌套在forloop中订阅）之后，for循环才应迭代

1 个答案: