angular - 如何在angular2中使用FormControl statusChanges？

Question

我是 angular2 的新手，我想在用户在下拉列表中选择某个值时触发一个函数。所以我尝试实现 FormControl 类的 statusChange 但它没有被触发，

wonder how and when to use the statusChange in angular2this is my code

class policy{
 subCategory: FormControl = new FormControl();
 ngOnInit() {
            this.subCategory.statusChanges.subscribe(
                s => {
                    alert('success');
                }, e => {
                    alert('error');
                }, () => {
                    alert('complete');
                }
            );
        }
}

我认为通过实现 statusChanges 我可以在下拉列表中的每次值更改时触发成功函数，显然它现在可以工作了。

更新 1

我已经更新了 plunkr

Answer 1

如评论所述，您可能需要 valueChanges。但是，对于通过搜索 statusChanges 的工作原理来到这里的成千上万的其他人来说，这里是:

this.subCategory.statusChanges.subscribe( (status) => {
  console.log(status); //status will be "VALID", "INVALID", "PENDING" or "DISABLED"
})

The docs描述这 4 个可能的值如下:

• VALID: This control has passed all validation checks.
• INVALID: This control has failed at least one validation check.
• PENDING: This control is in the midst of conducting a validation check.
• DISABLED:This control is exempt from validation checks. These status values are mutually exclusive, so a control cannot be both valid AND invalid or invalid AND disabled.