Data Binding in Angular using TypeScript Classes

Question

Data Binding in Angular using TypeScript Classes

Within my component, I have defined a property that is linked to the UI.

Component

export class MyComponent implements OnInit {

    public propertyA: string;
    public propertyB: string;

}

UI

<textarea matInput rows="10" 
placeholder="Body" [(ngModel)]="formData.propertyA" 
[ngModelOptions]="{standalone: true}"></textarea>

How can I achieve something like this:

export class MyComponent implements OnInit {

    public propertyA: string = "Some text with {{propertyB}} bound.";
    public propertyB: string;

}

Essentially, I want propertyA to be bound to the textbox, and nested within propertyA is the value of propertyB, which updates dynamically based on another databinding.

angular typescript

Answer 1

Answer №1

class NewComponent extends Component {

let message:string = `Using template literals can make your code more readable than concatenation.`;
let name:string;

}

If you want to learn more, check out this template literals guide.

Answer 2

class NewComponent extends Component {

let message:string = `Using template literals can make your code more readable than concatenation.`;
let name:string;

}

If you want to learn more, check out this template literals guide.

Answer 3

Answer №2

If we want to maintain the synchronization between propertyA and propertyB, not just calculate it initially:

Using Getters

The simplest approach is to use getters. It's important to note that using getter/functions in a template will trigger its execution during every Change Detection cycle (keep this logic as straightforward as possible).

export class MyComponent implements OnInit {

    public get propertyA(): string {
        `Some text with ${this.propertyB} bound.`;
    };
    public propertyB: string;

}

Using Observable

A more efficient method is to utilize Observables for values that can evolve over time.

export class MyComponent implements OnInit {

    public propertyA = this.propertyB.pipe(
        map(propertyB => `Some text with ${propertyB} bound.`),
    );
    // BehaviorSubject is a Subject that holds an initial value and persists the last value
    public propertyB: Observable<string> = new BehaviorSubject('');

    // somewhere
    foo(){
        this.propertyB.next('New value');
    }
}

// template
<div>propertyA: {{propertyA | async}}</div>
<div>propertyB: {{propertyB | async}}</div>

Answer 4

If we want to maintain the synchronization between propertyA and propertyB, not just calculate it initially:

Using Getters

The simplest approach is to use getters. It's important to note that using getter/functions in a template will trigger its execution during every Change Detection cycle (keep this logic as straightforward as possible).

export class MyComponent implements OnInit {

    public get propertyA(): string {
        `Some text with ${this.propertyB} bound.`;
    };
    public propertyB: string;

}

Using Observable

A more efficient method is to utilize Observables for values that can evolve over time.

export class MyComponent implements OnInit {

    public propertyA = this.propertyB.pipe(
        map(propertyB => `Some text with ${propertyB} bound.`),
    );
    // BehaviorSubject is a Subject that holds an initial value and persists the last value
    public propertyB: Observable<string> = new BehaviorSubject('');

    // somewhere
    foo(){
        this.propertyB.next('New value');
    }
}

// template
<div>propertyA: {{propertyA | async}}</div>
<div>propertyB: {{propertyB | async}}</div>

Data Binding in Angular using TypeScript Classes

Answer №1

Answer №2

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