合并两个RxJS Observables / Subscriptions并遍历其数据

Question

我使用Angular（版本7）和RxJS并进行两次api调用，每次调用返回一个observable，然后我订阅。

现在我必须组合这些订阅，因为来自两个observable的数据是相互依赖的，我需要它们来实现某些功能（例如，一个过滤器检查从subcription2接收的id是否出现在subscription1中，然后只返回一些东西......）。

由于我的代码很长，我已经准备了一个较小的样本版本并标记了重要的地方给我评论：

getSomething(){
    /**
     * anIdFromSubscriptionTwo: An id that I need from subscription2
     */
    const subscription1 = this.service.getSomeStuff().subscription((someStuff) => {
        this.someStuff = stuff;
        this.someStuff.forEach((stuff) => {
            if(stuff.someProperty !== null && stuff.id === anIdFromSubscriptionTwo){
                ...
            }
        });
    } 

    /**
     * aIdFromSubscriptionOne: An id of type string that I get in the forEach loop inside of subscription1
     * aTypeFromSubscriptionOne: A type of type string that I get in the forEach loop inside of subscription1
     */
    const subscription2 = this.service.getSomeOtherStuff(aIdFromSubscriptionOne: string, aTypeFromSubscriptionOne: string).subscription((someOtherStuff) => {
        this.someOtherStuff = someOtherStuff;
        this.someOtherStuff.forEach(() => {
            // This is the only if statement I need, after combining the two subscriptions
            if(subscription1.stuff.someProperty !== null && subscription1.stuff.id === someOtherStuff.id){
                const properties: Image = {
                    id: // an id I need from subscription1
                    class: // a class I need from  subscription1
                    type: // a type I need from subscription2
                    ref: // a reference to the image url from subscription2
                    ...
                }
            }
        })  
    });
}

如何组合这两个订阅，以便我可以在forEach循环中访问它们的数据并进行比较或一般使用？

Answer 1

你使用switchMap来避免在另一个内部订阅

import { switchMap } from 'rxjs/operators';


  this.service.getSomeStuff().pip(switchMap((someStuff) => {
        this.someStuff = someStuff;

      this.service.getSomeOtherStuff(aIdFromSubscriptionOne: string, aTypeFromSubscriptionOne: string)
       ).subscribe((someOtherStuff) => {
        this.someOtherStuff = someOtherStuff;
        this.someOtherStuff.forEach(() => {
        // make a foreach loop here on someStuff to check if someOtherStuff exist in some Stuff
          this.someStuff.foreach((somestuff) => {
             if(somestuff.someProperty !== null && somestuff.id === someOtherStuff.id){
               const properties: Image = {
                id: // an id I need from subscription1
                class: // a class I need from  subscription1
                type: // a type I need from subscription2
                ref: // a reference to the image url from subscription2
                ...
               }
             }
           });  
         }); 
      });   
  });