订阅角6

Question

toppings : Array
toppings2 : Array

我有两个订阅方法：

this.toppings.valueChanges.subscribe(val=> { 
console.log(val);
}

this.toppings2.valueChanges.subscribe(val2=> { 
console.log(val2);
}

我想在相同的字体中使用val和val2。我怎样才能在同一个地方获得val和val2？(或val3= val+val2)

Answer 1

zip组合了两个可观测值，并等待它们发出。combineLatest也会做得很好，你需要的并不重要，

zip(this.toppings.valueChanges, this.toppings2.valueChanges).subscribe(val => console.log(val[0] + val[1]))

Answer 2

combineLatest将为您提供最新版本的toppings和toppings2。

https://www.learnrxjs.io/operators/combination/combinelatest.html

大理石图：http://rxmarbles.com/#combineLatest

示例：

import {combineLatest} from 'rxjs';

combineLatest(this.toppings.valueChanges, this.toppings2.valueChanges )
                          .subscribe( ([topping1val, topping2val]) => {
                                      let topping3 = topping1val + topping2val;
                                 });