angular-docs-cn/public/docs/js/latest/api/di/Injector-class.jade

p.location-badge.
  exported from <a href='../di'>angular2/di</a>
  defined in <a href="https://github.com/angular/angular/tree/master/modules/angular2/src/di/injector.ts#L27-L261">angular2/src/di/injector.ts (line 27)</a>

:markdown
  A dependency injection container used for resolving dependencies.
  
  An `Injector` is a replacement for a `new` operator, which can automatically resolve the
  constructor dependencies.
  In typical use, application code asks for the dependencies in the constructor and they are
  resolved by the `Injector`.
  
  ## Example:
  
  Suppose that we want to inject an `Engine` into class `Car`, we would define it like this:
  
  ```javascript
  class Engine {
  }
  
  class Car {
    constructor(@Inject(Engine) engine) {
    }
  }
  
  ```
  
  Next we need to write the code that creates and instantiates the `Injector`. We then ask for the
  `root` object, `Car`, so that the `Injector` can recursively build all of that object's
  dependencies.
  
  ```javascript
  main() {
    var injector = Injector.resolveAndCreate([Car, Engine]);
  
    // Get a reference to the `root` object, which will recursively instantiate the tree.
    var car = injector.get(Car);
  }
  ```
  Notice that we don't use the `new` operator because we explicitly want to have the `Injector`
  resolve all of the object's dependencies automatically.
  
.l-main-section
  h2 Members
  .l-sub-section
    h3 constructor

    
    pre.prettyprint
      code.
        constructor(bindings: List&lt;ResolvedBinding&gt;, parent: Injector, defaultBindings: boolean)
    
    :markdown
      @param `bindings` A sparse list of <a href='ResolvedBinding-class.html'><code>ResolvedBinding</code></a>s. See `resolve` for the
      <a href='Injector-class.html'><code>Injector</code></a>.
      @param `parent` Parent Injector or `null` if root Injector.
      @param `defaultBindings` Setting to true will auto-create bindings. (Only use with root
      injector.)
      
      




  .l-sub-section
    h3 asyncGet

    
    pre.prettyprint
      code.
        asyncGet(token)
    
    :markdown

      Retrieves an instance from the injector asynchronously. Used with asynchronous bindings.
      
      @param `token`: usually a `Type`. (Same as token used while setting up a binding).





  .l-sub-section
    h3 createChildFromResolved

    
    pre.prettyprint
      code.
        createChildFromResolved(bindings: List&lt;ResolvedBinding&gt;)
    
    :markdown

      Creates a child injector and loads a new set of <a href='ResolvedBinding-class.html'><code>ResolvedBinding</code></a>s into it.
      
      @param `bindings`: A sparse list of <a href='ResolvedBinding-class.html'><code>ResolvedBinding</code></a>s.
      See `resolve` for the <a href='Injector-class.html'><code>Injector</code></a>.





  .l-sub-section
    h3 get

    
    pre.prettyprint
      code.
        get(token)
    
    :markdown

      Retrieves an instance from the injector.
      
      @param `token`: usually the `Type` of an object. (Same as the token used while setting up a
      binding).





  .l-sub-section
    h3 getOptional

    
    pre.prettyprint
      code.
        getOptional(token)
    
    :markdown

      Retrieves an instance from the injector.
      
      @param `token`: usually a `Type`. (Same as the token used while setting up a binding).





  .l-sub-section
    h3 parent

    
    :markdown

      Direct parent of this injector.
      
      





  .l-sub-section
    h3 resolveAndCreateChild

    
    pre.prettyprint
      code.
        resolveAndCreateChild(bindings: List&lt;Type | Binding | List&lt;any&gt;&gt;)
    
    :markdown

      Creates a child injector and loads a new set of bindings into it.
      
      A resolution is a process of flattening multiple nested lists and converting individual
      bindings into a list of <a href='ResolvedBinding-class.html'><code>ResolvedBinding</code></a>s. The resolution can be cached by `resolve`
      for the <a href='Injector-class.html'><code>Injector</code></a> for performance-sensitive code.
      
      @param `bindings` can be a list of `Type`, <a href='Binding-class.html'><code>Binding</code></a>, <a href='ResolvedBinding-class.html'><code>ResolvedBinding</code></a>, or a
      recursive list of more bindings.