Using the values (A: true, B: true) as a reference, I am looking to display radio buttons within an Angular framework

I'm a beginner with Angular and facing an issue with showing radio buttons based on server response. The 'checked' attribute seems to not work as expected.

My goal is to display two radio buttons under one label - "Allow" and "Deny". The server response looks like this: {"math": true, "science": false, "language": true}. I want the 'Allow' radio button checked for all true values and the 'Deny' button checked for false value. This is what I've been attempting:

radio-button.component.html

<form [formGroup]= subjectGroup (ngsubmit)="onSubmit()">
<div class="form-group row">
<label for="maths" class="col-sm-4 col-form-label text-dark">
<b>Maths</b></label>
<div class="form-check form-check-inline">
<input id="allow" type="radio" value="allow" name="screenCapture" formControlName="mathsValue"(click)="changeValue('maths', true)" checked="'response.maths' == true">
<label for="allow">Allow</label>
</div>
<div class="form-check form-check-inline">
<input id="deny" type="radio" value="deny" name="screenCapture" formControlName="mathsValue" (click)="changeValue('maths', false)"
checked="'response.maths' == false">
<label for="deny">Deny</label>
</div>
</div>
<button class="btn btn-success>Update</button>

radio-button.component.ts

import { FormBuilder, FormControl, FormGroup, Validators } from '@angular/forms';

@Component({
  selector: 'app-radio-button',
  templateUrl: './radio-button.component.html',
  styleUrls: ['./radio-button.component.css']
})

export class RadioButtonComponent implements OnInit {
public response;
public subjectGroup: FormGroup;


ngOnInit(): void {
this.getResponse();
this.form();
}

getResoponse(){
 // Storing all the server response data in a global variable (response)
}

form(){
this.subjectGroup = this.fb.group({
maths: new FormControl('')
})

changeValue(e, value) {
(this.response[e]) = value
  }

}

I need help with code snippets for correctly checking the 'Allow' button for true values and the 'Deny' button for false values in Angular.

Answer №1

In the provided example, it appears as if the attribute is set to

checked="'response.maths' == true"
.

If you examine your DOM closely, you will see that this string is literally present in your element. To ensure that Angular evaluates it as a valid code expression, you should either use [checked] or {{'response.maths' == true}}.

However, for your specific scenario, neither of these options would work because you are essentially checking if the string 'response.maths' equals true, which it does not. (Although using == instead of

===</code may result in it being treated as true due to JS's truthy concept).</p>
<p>The correct approach would be much simpler: <code>[checked]="response.maths"
.

Since response.maths is already a boolean value, you can directly utilize it without any complex comparison.

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