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.

https://i.sstatic.net/AwcII.png

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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