合並兩個RxJS Observables / Subscriptions並遍歷其數據

Question

我使用Angular （版本7）和RxJS並進行兩次api調用，每次調用返回一個observable，然后我訂閱。

現在我必須組合這些訂閱，因為來自兩個observable的數據是相互依賴的，我需要它們來實現某些功能（例如，一個過濾器檢查從subcription2接收的id是否出現在subscription1中，然后只返回一些東西......）。

由於我的代碼很長，我已經准備了一個較小的樣本版本並標記了重要的地方給我評論：

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
                    ...
                }
            }
        })  
    });
}

如何組合這兩個訂閱，以便我可以在forEach循環中訪問它們的數據並進行比較或一般使用？

Answer 1

你使用switchMap來避免在另一個內部訂閱

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
                ...
               }
             }
           });  
         }); 
      });   
  });