@angular/core

ContentChildren

decorator

Property decorator that configures a content query.

class ContentChildren {
}

Property decorator that configures a content query.

Use to get the QueryList of elements or directives from the content 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.

Content queries are set before the ngAfterContentInit callback is called.

Does not retrieve elements or directives that are in other components' templates, since a component's template is always a black box to its ancestors.

Metadata Properties:

selector - The directive type or the name used for querying.
descendants - If true include all descendants of the element. If false then only query direct children of the element.
emitDistinctChangesOnly - The QueryList#changes observable will emit new values only if the QueryList result has changed. When false the changes observable might emit even if the QueryList has not changed. ** Note: *** This config option is deprecated, it will be permanently set to true and removed in future versions of Angular.
read - Used to read a different token from the queried elements.

The following selectors are supported.

Any class with the @Component or @Directive decorator
A template reference variable as a string (e.g. query <my-component #cmp></my-component> with @ContentChildren('cmp'))
Any provider defined in the child component tree of the current component (e.g. @ContentChildren(SomeService) someService: SomeService)
Any provider defined through a string token (e.g. @ContentChildren('someToken') someTokenVal: any)
A TemplateRef (e.g. query <ng-template></ng-template> with @ContentChildren(TemplateRef) template;)

In addition, multiple string selectors can be separated with a comma (e.g. @ContentChildren('cmp1,cmp2'))

The following values are supported by read:

Any class with the @Component or @Directive decorator
Any provider defined on the injector of the component that is matched by the selector of this query
Any provider defined through a string token (e.g. {provide: 'token', useValue: 'val'})
TemplateRef, ElementRef, and ViewContainerRef

Here is a simple demonstration of how the ContentChildren decorator can be used.

Tab-pane example

Here is a slightly more realistic example that shows how ContentChildren decorators can be used to implement a tab pane component.

descendants

boolean

emitDistinctChangesOnly

boolean

first

boolean

read

any

isViewQuery

boolean

selector

any

static

boolean