Identify modifications to properties in Angular

What is the most effective method for responding to property changes within a component? I am seeking a solution that will trigger a specific function every time a property in a component is altered. Consider the following example with a single component:

@Component({selector: 'component', template: '{{name}} {{number}}'})
class singleComp {
  name: string = 'Old';
  number: number = 1;

  changeProperties() {
    this.name = 'New';
    this.number = 2;
  }

  changesDetected() {
    console.log('Changes detected');
  }
}

In the scenario presented above, the singleComp has two properties - name and number. While calling changesDetected() from changeProperties() could be a solution, it might not be practical if there are multiple methods affecting the component's properties. Manually adding changesDetected() at the end of each property-modifying method could result in multiple calls from various methods.

I have attempted to detect changes using OnChanges and AfterContentChecked, but these approaches do not fully capture all internal property modifications within a component.

In simple terms, I am looking for a way to automatically execute the changesDetected() function whenever any internal property of the component is modified.

edit

While it is possible that ngDoCheck can identify internal changes, implementing it may also lead to tracking changes in external components, making it less suitable for monitoring changes strictly at a component level.

Answer №1

Consider utilizing the EventEmitter in this scenario.

What is the most effective method to respond to changes in component properties? I am seeking a way to execute a function every time a property within a component undergoes a modification. Take a look at this example of a single component:

@Component({selector: 'component', template: '{{name}} {{number}}'})
class singleComp {
  name: string = 'Old';
  number: number = 1;
  private propertiesChanged: EventEmitter<any> = new EventEmitter();
  private _score: number;

  get score():boolean {
    return this._score;
  }

  set score(s:number) {
    this._score = s;
    this.propertiesChanged.emit(s);
  }

  constructor() {
     this.propertiesChanged.subscrive(() => this.changesDetected());
  }
  changeProperties() {
    this.name = 'New';
    this.number = 2;
    this.propertiesChanged.emit({}); // you can pass any object here, chanegd properties as well.
  }

  changesDetected() {
    console.log('Changes detected');
  }

}

You can also trigger a change event in the setter of these properties, depending on what suits your specific situation best. Consider the implementation with the score property.

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