Do [(ngModel)] bindings strictly adhere to being strings?

Imagine a scenario where you have a radiobutton HTML element within an angular application,

  <div class="radio">
    <label>
      <input type="radio" name="approvedeny" value="true" [(ngModel)]=_approvedOrDenied>
      Approve
    </label>
  </div>

Within our component, the _approvedOrDenied property is defined as a boolean.

@Component({   
export class ApprovalsComponent implements OnInit {
  _approvedOrDenied: boolean;

Surprisingly, during debugging of the clientside code, it was observed that this property was being set as a string. There are no explicit casts in the code that could lead to this behavior, suggesting that Angular might be automatically converting it.

Do all databound properties get converted to strings in Angular? If so, then what purpose does specifying the type _approvedOrDenied: boolean serve in typescript?

javascriptangulartypescript

Answer №1

Not all cases involve strings. Also, it's interesting to see a tag without quotes for the first time!

For instance, when creating a component with an input like this 

<app-my-component firstVariable="hello world"></app-my-component>

The value is considered as a string. You cannot provide a variable in this scenario; rather, the input will take the name of the variable as its value.

However, if you do this 

<app-my-component [firstVariable]="hello world"></app-my-component>

This approach will not function. In this case, you are expected to supply a variable. To resolve this issue, utilize the following method 

<app-my-component [firstVariable]="'Hello world'"></app-my-component>

By doing so, you are essentially providing an "anonymous variable": using quotes lets Angular recognize it as a string.

In your situation, a radio button is utilized. Radio buttons belong to groups and each has string values. Therefore, even if you input true, it does not automatically become a boolean! If you desire to assign a boolean value, you must use 

[value]="true"

Hopefully, this clarifies any confusion!

Answer №2

To get the desired outcome, simply delete value="true" from the HTML code.

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