Angular 4 Select不要在ngModel更改时更新 [英] Angular 4 Select don't update on ngModel change

问题描述

我试图确保在选择新值之后，我调用eventChange()函数并将所选值恢复为默认值.但是会发生什么:ngModel值更新，但是所选值保持不变.我应该如何将所选值和ngModel值设置为相同?

I am trying to make that after new value is selected, I call eventChange() function and restore selected value to default. But what happens: ngModel value updates, but selected value stays the same. How should I do that selected value and ngModel value would be the same?

HTML文件

<select [(ngModel)]="selectedValue"
       (change)="eventChange()"

>
      <option [disabled]="true"
              [ngValue]="-1">
        Choose an option
      </option>
      <option *ngFor="let item of myList index as i"
              [ngValue]="i"
      >
        {{item.name}}
      </option>
</select>

组件文件中的功能

selectedValue = -1; //works //Option in select is changed
eventChange(){
    this.selectedValue= -1; //don't work 
    //Function is called, 
    //Value changes
    //But selected Option in Select doesn't change
}

评论: 在运行的网页上(刷新)，正确设置了select的第一个值，如果我在组件文件中将变量 selectedValue 设置为其他索引，则选择了另一个值，但它仅在运行时起作用，而在功能上不起作用)

Comment: On running web page(refresh) first value of select is set properly, if in component file I set variable selectedValue to other index the other value is selected, but it works only on run, but not in function)

我也发现了这个问题 Angularjs:选择何时不更新ng-model已更新 但这是对AngularJS使用ng-options而不是ng-repeat的答案，在角度4中，我只发现* ngFor ...

Also I found this question Angularjs: select not updating when ng-model is updated But here is an answer to AngularJS for using ng-options, instead of ng-repeat, in angular 4 I found only *ngFor...

更新: 澄清以防万一:正在调用函数，但是我想通过javascript更改所选的选项.我通过更改ngModel值来尝试此操作，但是即使更改ngModel值，所选选项也不会更改.

Update: Clarification just in case: function is being called, but I want change selected option through javascript. I try this by changing ngModel value, but even when ngModel value is cahnged, selected option doesn't change.

推荐答案

使用 ngModelChange ，您无需 [ngValue]

Use ngModelChange and you don't need [ngValue]

<select [(ngModel)]="selectedValue"
       (ngModelChange)="eventChange()"

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