Stop any modifications to the input data

We are currently in the process of building an angular application with Angular 5.

Typically, our components have input and output parameters defined as shown below:

export class MultipleItemPickerComponent implements OnInit {
  @Input() itemPickerHeaderText: string;
  @Output() multipleItemsPickerOkClick: EventEmitter<string[]> = new EventEmitter();
  @Output() multipleItemsPickerCancelClick: EventEmitter<Event> = new EventEmitter();

In the template file for this component, it is used in the following manner:

<app-multiple-item-picker itemPickerHeaderText="{{question.texts['reason']}}" (multipleItemsPickerOkClick)="multipleReasonsPickerOkClick($event)" (multipleItemsPickerCancelClick)="multipleReasonsPickerCancelClick($event)"></app-multiple-item-picker>

Everything runs smoothly as intended.

However, there is a possibility within the same class to modify the input value to something other than its original value.

removeItemClick() {
    this.itemPickerHeaderText = "something completely different";
}

I am seeking a way to prevent any alterations to the input values. Is there a solution for this?

Answer №1

To prevent updating the input value from outside the constructor, you can designate the input property as readonly in TypeScript. This will restrict modifications to the input value within the class.

@Input() 
public readonly itemPickerHeaderText: string;

This method may seem unconventional, but it effectively achieves the desired outcome. The Angular compiler recognizes the property as read-only, while the TypeScript compiler ensures its integrity despite being bound to an Angular input.

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