加入两个firebase observables

Question

我正在使用angularfiredatabase。我正在尝试加入我的产品和我的产品分支。我想从我的产品分支获得数量到产品。继承人的Database 0有我的分支

findAllProductsForBranch(branchName:string):Observable<any[]> { 

    const products$ = this.findProductsByProductKeys(this.findProductKeysPerBranch(branchName)); 
    products$.map((products) => { 
    products.forEach((product) => { 
     product.map((product) => { 
     Object.assign(product, 
     { 
      quantity: 
      this.db.object(`/products-branch/0/${product.$key}`) 
      .switchMap(product => product._quantity) 
     }) 
     }) 
    }); 
    //return products; 
    }) 
    .do(console.log) 
    .subscribe(); 
    return Observable.of([]); 
} 

产品$的键包含一个可观察的产品没有数量，所以我想添加量，但问题是如何？当我运行这个未定义的代码显示在控制台中。林坚持在这里呆了近一个星期

Answer 1

我找到了答案，我的问题，这要归功于cartant他解释说在这里Fork join two firebase observables

findAllProductsForBranch(branchName:string, branchKey: string):Observable<any[]> { 
    const products$ = this.findProductsByProductKeys(this.findProductKeysPerBranch(branchName)); 
    return products$.mergeMap((products) => { 
     return Observable.forkJoin(
      // Map the tours to the array of observables that are to 
      // be joined. Note that forkJoin requires the observables 
      // to complete, so first is used. 

      products.map((product) => this.db 
       .object(`/products-branch/${branchKey}/${product.$key}`) 
       .first() 
      ), 

      // Use forkJoin's results selector to match up the result 
      // values with the tours. 

      (...values) => { 
       products.forEach((product, index) => { product._quantity = values[index]._quantity; }); 
       return products; 
      } 
     ); 
    }); 
}