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Exploring the Various Decorators in Angular – Netanel Basal

  • Exploring the Various Decorators in Angular@Attribute —Returns the value of the specified attribute from the host@ViewChildren—Returns the specified elements or directives from the view DOM as QueryListconsole.log() outputQueryList is just a fancy name for an object that stores a list of items.
  • Any time a child element is added, removed, or moved, the query list will be updated, and the changes observable of the query list will emit a new value.Things to Remember —The QueryList is initialized only before the ngAfterViewInit lifecycle hook, therefore, is available only from this point.ViewChildren don’t include elements…
  • @ContentChild —Like ContentChildren but returns only the first element or the directive matching the selector from the content DOM@HostBinding —Declares a host property bindingIn the third example Angular will add type=”text” to our host because when you don’t provide a parameter the class property name is used.@HostListener —Declares a host listener.
  • Angular will invoke the decorated method when the host element emits the specified eventThis decorator also support adding events to the globals window, document, and body with this syntax — global:event.@Self —The @Self decorator tells DI to look for a dependency only from itself, so it will not walk up the treeconsole.log() outputIf…
  • The injector provides null if the dependency is not found.In our example, the dependency property will be null because we don’t register the OptionalDependency provider in any injector.@Inject —A parameter decorator that specifies a dependency@Injectable —Let’s Angular know that a class can be used with the DIRemember that this decorator is not…

QueryList is just a fancy name for an object that stores a list of items. What is special about this object is when the state of the application changes Angular will automatically update the object…

Exploring the Various Decorators in Angular@Attribute —Returns the value of the specified attribute from the host@ViewChildren—Returns the specified elements or directives from the view DOM as QueryListconsole.log() outputQueryList is just a fancy name for an object that stores a list of items. What is special about this object is when the state of the application changes Angular will automatically update the object items for you.QueryList implements an iterable interface, therefore, it can be used in Angular templates with the ngFor directive. ( you can read more about this topic here )QueryList API —Getters —first — get the first itemlast — get the last itemlength — get the lengthMethods —map(), filter() , find(), reduce(), forEach(), some().toArray() — returns the items as javascript arraychanges() — Changes can be observed by subscribing to the changes Observable. Any time a child element is added, removed, or moved, the query list will be updated, and the changes observable of the query list will emit a new value.Things to Remember —The QueryList is initialized only before the ngAfterViewInit lifecycle hook, therefore, is available only from this point.ViewChildren don’t include elements that exist within the ng-content tag.The read parameter —By default, the ViewChildren decorator will return the component instance, but you can ask for other { read: ElementRef }) alerts: outputViewContainerRef — You need this token when you need to create templates or components { read: ViewContainerRef }) alerts: output@ViewChild—Like ViewChildren but returns only the first element or the directive matching the selector from the view DOMYou can see that you also can use a local variable from your template to get a reference to…

Exploring the Various Decorators in Angular – Netanel Basal

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