Host class

Specifies that an injector should retrieve a dependency from any injector until reaching the closest host.

In Angular, a component element is automatically declared as a host for all the injectors in its view.

Example

In the following example App contains ParentCmp, which contains ChildDirective. So ParentCmp is the host of ChildDirective.

ChildDirective depends on two services: HostService and OtherService. HostService is defined at ParentCmp, and OtherService is defined at App.

class OtherService {}
class HostService {}

@Directive(
  selector: 'child-directive'
)
class ChildDirective {
  ChildDirective(
      @Optional() @Host() OtherService os,
      @Optional() @Host() HostService hs) {
    print("os is null", os);
    print("hs is NOT null", hs);
  }
}

@Component(
  selector: 'parent-cmp',
  providers: const [HostService],
  template: '''
    Dir: <child-directive></child-directive>
  ''',
  directives: const [ChildDirective]
)
class ParentCmp {}

@Component(
  selector: 'app',
  providers: const [OtherService],
  template: '''
    Parent: <parent-cmp></parent-cmp>
  ''',
  directives: const [ParentCmp]
)
class App {}

bootstrap(App);

Annotations

• @Target({TargetKind.parameter})

Constructors

Host()

const

Properties

hashCode → int

The hash code for this object.

no setter, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited