How can I associate labels with form fields outside them in Angular?

问题

Let's say I'm creating labels and form fields in a *ngFor loop like this:

app.component.ts

export class AppComponent  {
  items = ['aaa', 'bbbbbb', 'ccccccccc']
}

app.component.html

<div class='form'>
  <ng-container *ngFor="let item of items">
    <label>{{item|uppercase}}:</label>
    <input [value]="item"/>
  </ng-container>
</div>

(See it on StackBlitz: https://stackblitz.com/edit/angular-ptwq6t)

Is there a way to cleanly associate these "dynamic" labels and inputs with one another? If I do:

<label for="field" >{{item|uppercase}}:</label>
<input id="field" [value]="item"/>

Angular just repeats the for and id attributes verbatim and all labels point to the first input field.

Is there some way to use Angular's component identity, or am I stuck with something like generating a UUID myself, or otherwise guaranteeing uniqueness of the ID myself?

I can't nest the input inside the label because I have to reuse some already implemented CSS that doesn't expect that structure, but would still like the better usability that comes from having a proper label.

回答1:

Given that the items are unique, you could surely do this:

<label [for]="item" >{{item|uppercase}}:</label>
<input [id]="item" [value]="item"/>

That way, each id and for would be unique and label would work as required.

Here is the demo.

If you anyway need to generate the unique IDs, take a look at shortid

回答2:

you can try:

 <div class='form'>
      <ng-container *ngFor="let item of items">
        <label for="{{item}} + 'field'" >{{item|uppercase}}:</label>
        <input id="{{item}} + 'field'" [value]="item"/>
      </ng-container>
 </div>

or use the ngfor index if your items are not unique:

<div class='form'>
  <ng-container *ngFor="let item of items; let i = index">
    <label for="{{i}} + 'field'" >{{item|uppercase}}:</label>
    <input id="{{i}} + 'field'" [value]="item"/>
  </ng-container>
</div>

DEMO

来源：https://stackoverflow.com/questions/53406626/how-can-i-associate-labels-with-form-fields-outside-them-in-angular

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