如何根据下拉列表中的选定值动态更改占位符的值? [英] how to dynamically change the value of placeholder upon the selected values in the drop down?

问题描述

我有一个下拉列表，其中包含:父亲，母亲和监护人.随后是一个没有占位符的输入文本框.我希望文本框的占位符根据所选的值动态更新

I have a drop down containing: father, mother and guardian. Followed by an input text-box with no placeholder on it. I wanted the placeholder of the text-box to update dynamically according to the value selected

我尝试使用为ts文件部分中的占位符属性分配字符串.但它只能选择该特定值.我希望它选择一个* ngIf

I tried using assigning a string to placeholder property in the ts file section. but it could only choose that particular value. i wanted it to choose with an *ngIf

this is the select drop-down

<mat-select placeholder="Relation to Student"formControlName="relationType">
    <mat-option *ngFor="let relation of relationType" [value]="relation">
         {{ relation }}
    </mat-option>
</mat-select>

this is the html input

<input matInput placeholder="{{related}} " formControlName="fatherFullName" required>

this is the ts and i know this isn't how it works. i'm sure of adding an "if" but i'm not sure of how to do it

related = ' Father's full name';

我期望这样的结果:如果在选择下拉列表中选择了父亲，则输入文本框中的占位符应为​​父亲的全名.

I'm expecting a result where if father is selected in the select drop-down, the placeholder in the input text-box should be Father's full name.

提前谢谢！

推荐答案

我想这就是你要的:

i guess this is what you asking for:

在您的html中

    <mat-form-field class="example-full-width">
    <input matInput placeholder="{{str}}" value="Sushi">
  </mat-form-field>

  <mat-form-field class="example-full-width">
    <mat-select [(ngModel)]="changeData" (ngModelChange)="test()" name="dropBox">
      <mat-option value="relation1">relation1</mat-option>
      <mat-option value="relation2">relation2</mat-option>
      <mat-option value="relation3">relation3</mat-option>
    </mat-select>
  </mat-form-field>

现在在您的ts文件中

str =  '';
changeData:any ;
test(){
  console.log("rest");
  this.str = this.changeData;
}

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