Check out this sample demo that I've put together.
In the code, I'm passing a value of ipNumber = '99'; to the component HelloComponent.
The issue arises with the @Input, which is defined as
@Input() someVal : number;
I aim to receive an error when a string is passed through @Input.
To resolve this, the correct input should be
ipNumber = 99;
Instead of
ipNumber = '99';
To ensure the validity of your input, consider utilizing the ngOnChanges Lifecycle hook.
ngOnChanges(changes: SimpleChanges) {
const typeOfName = typeof changes['name'].currentValue;
if (typeOfName !== 'string') {
console.warn(`You provided ${typeOfName} instead of a string as expected`);
}
}
For more information, refer to this article:https://medium.com/@abdelelmedny/angular-input-decorators-5d38089070aa
Placing the code inside the constructor will not be effective since the angular component's life cycle has not reached that point yet. It would be better to place it in the ngOnInit method or a separate function that can be called within the ngOnInit or any subsequent life cycle event.
Please refer to the code snippet below:
ngOnInit() {
if(typeof this.someVal !== 'number') {
console.error("This is not a number");
}
}
One effective method to verify the type of an @Input is by utilizing JavaScript's typeof function. This allows us to determine whether the provided value is a number or not, enabling us to handle errors accordingly.
export class HelloComponent implements OnInit {
@Input() name: string;
@Input() someVal : number;
constructor(){
}
ngOnInit() {
console.log(this.someVal)
if(typeof this.someVal !== "number" ) {
throw new Error('Please provide only number');
}
}
}
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