Lifecycle hooks in Angular

Angular, a robust framework for building dynamic web applications, offers developers a range of lifecycle hooks that provide valuable insights into the lifecycle hooks of Angular components. These hooks enable developers to execute custom logic at specific stages of a component’s lifecycle, enhancing control and flexibility. Let’s explore how you can utilize Angular lifecycle hooks in your projects and delve into their essence.

 

1. ngOnChanges(): The ngOnChanges() method is called when one or more input properties of a component change. It provides a hook for responding to changes in input properties and performing additional logic based on the changes.

ngOnChanges(changes: SimpleChanges) {
  // Respond to changes in input properties
  if (changes.data) {
    this.processData();
  }
}

 

2. ngOnInit(): The ngOnInit() method is invoked after Angular has initialized all data-bound properties of a component. Developers commonly use it to initialize component properties and fetch initial data from external sources.

ngOnInit() {
  // Initialize component properties
  this.loadData();
}

 

3. ngDoCheck: During every change detection cycle, Angular calls the ngDoCheck hook, enabling developers to perform custom change detection logic.

export class MyComponent implements DoCheck {
  ngDoCheck() {
    console.log('Change detection cycle triggered');
  }
}

 

4. ngAfterContentInit: Angular calls the ngAfterContentInit hook after projecting external content into the component’s view. Developers commonly use it for initialization that depends on content projection.

export class MyComponent implements AfterContentInit {
  ngAfterContentInit() {
    console.log('External content projected into component');
  }
}

 

5. ngAfterViewInit: Angular calls the ngAfterViewInit hook after initializing the component’s views and child views.

export class MyComponent implements AfterViewInit {
  ngAfterViewInit() {
    console.log('Component views initialized');
  }
}

 

6. ngOnDestroy: Angular calls the ngOnDestroy hook just before destroying the component. Developers commonly use it for cleanup tasks, such as unsubscribing from observables or releasing resources.

export class MyComponent implements OnDestroy {
  ngOnDestroy() {
    console.log('Component destroyed');
  }
}

 

Conclusion:

By understanding and leveraging these lifecycle hooks, developers can enhance the functionality and performance of their Angular components. Each hook provides a specific opportunity to perform tasks at different stages of the component lifecycle, ensuring better control and optimization of Angular applications.