ViewChild is used to select an element from component’s template while ContentChild is used to select projected content.
Besides, What is the difference between ViewChild and ViewChildren?
Another critical difference is that @ViewChild returns a single native DOM element as a reference, while the @ViewChildren decorator returns the list of different native DOM elements in the form of QueryList , which contains the set of elements.
Keeping this in mind, What is ContentChild? ContentChildren is a parameter decorator that is used to fetch the QueryList of elements or directives from the content DOM. The QueryList is updated whenever the child element/component is added or removed.
What is ContentChild and ContentChildren?
The ContentChild & ContentChildren are decorators, which we use to Query and get the reference to the Projected Content in the DOM. Projected content is the content that this component receives from a parent component. The ContentChild & ContentChildren is very similar to the ViewChild & ViewChildren.
What does ViewChild return?
The ViewChild or ViewChildren decorators are used to Query and get the reference of the DOM element in the Component. ViewChild returns the first matching element and ViewChildren returns all the matching elements as a QueryList of items. We can use these references to manipulate element properties in the component.
What is ViewChild and ViewChildren in Angular?
The @ViewChild and @ViewChildren decorators in Angular provide access to child elements in the view DOM by setting up view queries. A view query is a requested reference to a child element within a component view which contains metadata of the element.
What is ViewChild for?
The @ViewChild decorator allows us to inject into a component class references to elements used inside its template, that’s what we should use it for. Using @ViewChild we can easily inject components, directives or plain DOM elements.
Why do we need ViewChild and ViewChildren in Angular?
ViewChild and ViewChildren can be used to access the properties and methods of the child component. … We will look into the code to access the child component’s properties and methods from the parent component using @ViewChild .
What is the use of ContentChild?
The @ContentChild and @ContentChildren decorators are used to fetch single child element or all child elements from content DOM. Let us understand more about it. @ContentChild gives the first element or directive matching the selector from the content DOM.
What is use of @ViewChild?
The @ViewChild decorator allows us to inject into a component class references to elements used inside its template, that’s what we should use it for. Using @ViewChild we can easily inject components, directives or plain DOM elements.
How do I use ngAfterContentInit?
When should you use ngAfterContentInit? Use ngAfterContentInit to call something once after all of the content has been initialized. ngAfterContentInit will run once after the first ngDoCheck().
What is difference between component and directive?
Component is used to break up the application into smaller components. But Directive is used to design re-usable components, which is more behavior-oriented. That is why components are widely used in later versions of Angular to make things easy and build a total component-based model.
What is renderer in Angular?
The Renderer is a class that is a partial abstraction over the DOM. Using the Renderer for manipulating the DOM doesn’t break server-side rendering or Web Workers (where direct access to the DOM would break). ElementRef is a class that can hold a reference to a DOM element.
What is ViewContainerRef?
ViewContainerRef represents a container where one or more views can be attached. The first thing to mention here is that any DOM element can be used as a view container. What’s interesting is that Angular doesn’t insert views inside the element, but appends them after the element bound to ViewContainer .
What is read in ViewChild?
With {read: SomeType} you tell what type should be returned from the element with the #myname template variable. If you don’t provide the read parameter, @ViewChild() returns the. ElementRef instance if there is no component applied, or the. component instance if there is.
Why is ViewChild null?
Sometimes, if the component isn’t yet initialized when you access it, you get an error that says that the child component is undefined. … However, even if you access to the child component in the AfterViewInit, sometimes the @ViewChild was still returning null. The problem can be caused by the *ngIf or other directive.
What is ViewChild static true?
The static option for @ViewChild() and @ContentChild() queries determines when the query results become available. With static queries (static: true), the query resolves once the view has been created, but before change detection runs.
What are decorators in Angular?
Decorators are a design pattern that is used to separate modification or decoration of a class without modifying the original source code. In AngularJS, decorators are functions that allow a service, directive or filter to be modified prior to its usage.
What is Ng container and ng template?
To sum up, ng-content is used to display children in a template, ng-container is used as a non-rendered container to avoid having to add a span or a div , and ng-template allows you to group some content that is not rendered directly but can be used in other places of your template or you code.
Why do we need template reference variables?
Template variables help you use data from one part of a template in another part of the template. Use template variables to perform tasks such as respond to user input or finely tune your application’s forms. A template variable can refer to the following: a DOM element within a template.
How does ViewChild work in angular?
ViewChildlink
Property decorator that configures a view query. The change detector looks for the first element or the directive matching the selector in the view DOM. If the view DOM changes, and a new child matches the selector, the property is updated.
What is the use of renderer in angular?
The Renderer class is a built-in service that provides an abstraction for UI rendering manipulations. For example, you need to set the focus on an input element, so you may be tempted to do something like: This works fine.
What is the use of ViewChildren in angular?
Use to get the QueryList of elements or directives from the view DOM. 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. View queries are set before the ngAfterViewInit callback is called.