Lifecycle Hooks

• Allow us to perform custom logic at various stages of a component's life span
• The most common use case is when data isn't immediately available in the constructor
• Implemented as class methods on the component class
• Should not be called directly except when writing unit tests
• The lifecycle interfaces are optional. We recommend adding them to benefit from TypeScript's strong typing and editor tooling
• ngOnChanges called when an input or output binding value changes
• ngOnInit called after the first ngOnChanges
• ngDoCheck handles developer's custom change detection
• ngAfterContentInit called after component content initialized
• ngAfterContentChecked called after every check of component content
• ngAfterViewInit called after component's view(s) are initialized
• ngAfterViewChecked called after every check of a component's view(s)
• ngOnDestroy called just before the directive is destroyed.

These lifecycle hooks are implicitly called. They should simply exist to delegate to some other functionality.