反应形式值更改如何仅观看2个字段[Angular2]

Question

如何只观看Angular ReactiveForm的2个字段？ 我的表格如下：

this.filter = this.fb.group({
            text: ['', []],
            bankCountry: ['', []],
            bankCity: ['', []]
        });

如何查看与最后两个字段相关的更改？

Answer 1

两种方式：

1，使用combineLatest：

http://reactivex.io/rxjs/class/es6/Observable.js~Observable.html#static-method-combineLatest

Observable.combineLatest( this.text.valueChanges, this.bankCountry.valueChanges ).subscribe(respArr => {
     console.log(respArr); //this is array with responses from both observables
});

2，使用过滤器：

http://reactivex.io/rxjs/class/es6/Observable.js~Observable.html#instance-method-filter

this.filter.valueChanges.filter((val) => /*filter predicate returning boolean*/).subscribe(val => {
    console.log(val);
});