p.location-badge.
  exported from <a href='../metadata'>angular2/metadata</a>
  defined in <a href="https://github.com/angular/angular/tree/2.0.0-alpha.36/modules/angular2/src/core/metadata/directives.ts#L848-L1048">angular2/src/core/metadata/directives.ts (line 848)</a>

:markdown
  Annotations provide the additional information that Angular requires in order to run your
  application. This module
  contains <a href='ComponentMetadata-class.html'><code>ComponentMetadata</code></a>, <a href='DirectiveMetadata-class.html'><code>DirectiveMetadata</code></a>, and <a href='ViewMetadata-class.html'><code>ViewMetadata</code></a>
  annotations, as well as
  the <a href='../di/Host-var.html'><code>Host</code></a> annotation that is used by Angular to resolve dependencies.
.l-main-section
  h2 Members
  .l-sub-section
    h3 OnInit

    
    :markdown
      Notify a directive when it has been checked the first time.
      
      This method is called right after the directive's bindings have been checked,
      and before any of its children's bindings have been checked.
      
      It is invoked only once.
      
      
      
      ```
      @Directive({
        selector: '[class-set]',
        lifecycle: [LifecycleEvent.OnInit]
      })
      class ClassSet {
        onInit() {
        }
      }
       ```
      
      





  .l-sub-section
    h3 OnDestroy

    
    :markdown
      Notify a directive whenever a <a href='ViewMetadata-class.html'><code>ViewMetadata</code></a> that contains it is destroyed.
      
      
      
      ```
      @Directive({
        ...,
        lifecycle: [LifecycleEvent.OnDestroy]
      })
      class ClassSet {
        onDestroy() {
          // invoked to notify directive of the containing view destruction.
        }
      }
      ```
      
      





  .l-sub-section
    h3 OnChanges

    
    :markdown
      Notify a directive when any of its bindings have changed.
      
      This method is called right after the directive's bindings have been checked,
      and before any of its children's bindings have been checked.
      
      It is invoked only if at least one of the directive's bindings has changed.
      
      :
      
      ```
      @Directive({
        selector: '[class-set]',
        properties: [
          'propA',
          'propB'
        ],
        lifecycle: [LifecycleEvent.OnChanges]
      })
      class ClassSet {
        propA;
        propB;
        onChanges(changes:{[idx: string, PropertyUpdate]}) {
          // This will get called after any of the properties have been updated.
          if (changes['propA']) {
            // if propA was updated
          }
          if (changes['propA']) {
            // if propB was updated
          }
        }
      }
       ```
      
      





  .l-sub-section
    h3 DoCheck

    
    :markdown
      Notify a directive when it has been checked.
      
      This method is called right after the directive's bindings have been checked,
      and before any of its children's bindings have been checked.
      
      It is invoked every time even when none of the directive's bindings has changed.
      
      
      
      ```
      @Directive({
        selector: '[class-set]',
        lifecycle: [LifecycleEvent.DoCheck]
      })
      class ClassSet {
        doCheck() {
        }
      }
       ```
      
      





  .l-sub-section
    h3 AfterContentInit

    
    :markdown
      Notify a directive when the bindings of all its content children have been checked the first
      time (whether they
      have changed or not).
      
      
      
      ```
      @Directive({
        selector: '[class-set]',
        lifecycle: [LifecycleEvent.AfterContentInit]
      })
      class ClassSet {
      
        afterContentInit() {
        }
      
      }
       ```
      
      





  .l-sub-section
    h3 AfterContentChecked

    
    :markdown
      Notify a directive when the bindings of all its content children have been checked (whether
      they
      have changed or not).
      
      
      
      ```
      @Directive({
        selector: '[class-set]',
        lifecycle: [LifecycleEvent.AfterContentChecked]
      })
      class ClassSet {
      
        afterContentChecked() {
        }
      
      }
       ```
      
      





  .l-sub-section
    h3 AfterViewInit

    
    :markdown
      Notify a directive when the bindings of all its view children have been checked the first time
      (whether they
      have changed or not).
      
      
      
      ```
      @Directive({
        selector: '[class-set]',
        lifecycle: [LifecycleEvent.AfterViewInit]
      })
      class ClassSet {
      
        afterViewInit() {
        }
      
      }
       ```
      
      





  .l-sub-section
    h3 AfterViewChecked

    
    :markdown
      Notify a directive when the bindings of all its view children have been checked (whether they
      have changed or not).
      
      
      
      ```
      @Directive({
        selector: '[class-set]',
        lifecycle: [LifecycleEvent.AfterViewChecked]
      })
      class ClassSet {
      
        afterViewChecked() {
        }
      
      }
       ```