A Comprehensive Overview of Angular Lifecycle Hooks

Angular Lifecycle Hooks are special methods that enable developers to respond to key events in the lifecycle of a component or directive. These hooks allow for the execution of code at specific points as components are created, updated, or destroyed, facilitating more efficient application development.

Key Concepts

• Lifecycle: The lifecycle of a component begins at its creation and concludes upon its destruction. Throughout this lifecycle, various events occur, which developers can respond to using lifecycle hooks.
• Hooks: These are methods that Angular invokes at different stages of a component's lifecycle, enabling developers to implement specific logic.

Main Lifecycle Hooks

Below are the primary lifecycle hooks in Angular:

• Called once after the first ngOnChanges.
• Ideal for initialization logic (e.g., fetching data).
• Called before ngOnInit and whenever one or more data-bound input properties change.
• Useful for reacting to changes in input properties.
• Called during every change detection run.
• Useful for detecting and acting upon changes that Angular doesn't catch.
• Called after Angular projects external content into the component's view.
• Good for handling content that comes from other components.
• Called after the projected content has been checked.
• Useful for responding to changes in projected content.
• Called after the component's view (and child views) has been initialized.
• Ideal for DOM manipulation or third-party library integration.
• Called after the view has been checked.
• Good for responding to changes in the component's view.
• Called just before Angular destroys the component.
• Ideal for cleanup logic (e.g., unsubscribing from services).

ngOnDestroy

ngOnDestroy() {
    // Cleanup logic here
}

ngAfterViewChecked

ngAfterViewChecked() {
    // Respond to view changes
}

ngAfterViewInit

ngAfterViewInit() {
    // Logic after the view is initialized
}

ngAfterContentChecked

ngAfterContentChecked() {
    // Respond to projected content changes
}

ngAfterContentInit

ngAfterContentInit() {
    // Logic after content has been projected
}

ngDoCheck

ngDoCheck() {
    // Custom change detection logic
}

ngOnChanges

ngOnChanges(changes: SimpleChanges) {
    // Respond to changes
}

ngOnInit

ngOnInit() {
    // Initialization code here
}

Conclusion

Understanding Angular Lifecycle Hooks is crucial for building efficient, responsive applications. By leveraging these hooks, developers can effectively manage a component's behavior and performance throughout its lifecycle.