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

p.location-badge.
  exported from <a href='../di'>angular2/di</a>
  defined in <a href="https://github.com/angular/angular/tree/3a0410a/modules/angular2/src/di/binding.ts#L305-L447">angular2/src/di/binding.ts (line 305)</a>

:markdown
  Helper class for the <a href='bind-function.html'><code>bind</code></a> function.
  
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  h2 Members
  .l-sub-section
    h3 constructor

    
    pre.prettyprint
      code.
        constructor(token)
    
    :markdown
      
      




  .l-sub-section
    h3 token

    
    :markdown

      
      





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    h3 toClass

    
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      code.
        toClass(type: Type)
    
    :markdown

      Binds an interface to an implementation / subclass.
      
      
      
      Because `toAlias` and `toClass` are often confused, the example contains both use cases for
      easy comparison.
      
      ```javascript
      
      class Vehicle {}
      
      class Car extends Vehicle {}
      
      var injectorClass = Injector.resolveAndCreate([
        Car,
        bind(Vehicle).toClass(Car)
      ]);
      var injectorAlias = Injector.resolveAndCreate([
        Car,
        bind(Vehicle).toAlias(Car)
      ]);
      
      expect(injectorClass.get(Vehicle)).not.toBe(injectorClass.get(Car));
      expect(injectorClass.get(Vehicle) instanceof Car).toBe(true);
      
      expect(injectorAlias.get(Vehicle)).toBe(injectorAlias.get(Car));
      expect(injectorAlias.get(Vehicle) instanceof Car).toBe(true);
      ```
      
      





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    h3 toValue

    
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      code.
        toValue(value)
    
    :markdown

      Binds a key to a value.
      
      
      
      ```javascript
      var injector = Injector.resolveAndCreate([
        bind(String).toValue('Hello')
      ]);
      
      expect(injector.get(String)).toEqual('Hello');
      ```
      
      





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    h3 toAlias

    
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      code.
        toAlias(aliasToken)
    
    :markdown

      Binds a key to the alias for an existing key.
      
      An alias means that we will return the same instance as if the alias token was used. (This is
      in contrast to `toClass` where a separet instance of `toClass` will be returned.)
      
      
      
      Becuse `toAlias` and `toClass` are often confused, the example contains both use cases for easy
      comparison.
      
      ```javascript
      
      class Vehicle {}
      
      class Car extends Vehicle {}
      
      var injectorAlias = Injector.resolveAndCreate([
        Car,
        bind(Vehicle).toAlias(Car)
      ]);
      var injectorClass = Injector.resolveAndCreate([
        Car,
        bind(Vehicle).toClass(Car)
      ]);
      
      expect(injectorAlias.get(Vehicle)).toBe(injectorAlias.get(Car));
      expect(injectorAlias.get(Vehicle) instanceof Car).toBe(true);
      
      expect(injectorClass.get(Vehicle)).not.toBe(injectorClass.get(Car));
      expect(injectorClass.get(Vehicle) instanceof Car).toBe(true);
      ```
      
      





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    h3 toFactory

    
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      code.
        toFactory(factoryFunction: Function, dependencies?: List&lt;any&gt;)
    
    :markdown

      Binds a key to a function which computes the value.
      
      
      
      ```javascript
      var injector = Injector.resolveAndCreate([
        bind(Number).toFactory(() => { return 1+2; }),
        bind(String).toFactory((v) => { return "Value: " + v; }, [Number])
      ]);
      
      expect(injector.get(Number)).toEqual(3);
      expect(injector.get(String)).toEqual('Value: 3');
      ```
      
      





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    h3 toAsyncFactory

    
    pre.prettyprint
      code.
        toAsyncFactory(factoryFunction: Function, dependencies?: List&lt;any&gt;)
    
    :markdown

      Binds a key to a function which computes the value asynchronously.
      
      
      
      ```javascript
      var injector = Injector.resolveAndCreate([
        bind(Number).toAsyncFactory(() => {
          return new Promise((resolve) => resolve(1 + 2));
        }),
        bind(String).toFactory((v) => { return "Value: " + v; }, [Number])
      ]);
      
      injector.asyncGet(Number).then((v) => expect(v).toBe(3));
      injector.asyncGet(String).then((v) => expect(v).toBe('Value: 3'));
      ```
      
      The interesting thing to note is that event though `Number` has an async factory, the `String`
      factory function takes the resolved value. This shows that the <a href='Injector-class.html'><code>Injector</code></a> delays
      executing of the `String` factory
      until after the `Number` is resolved. This can only be done if the `token` is retrieved using
      the `asyncGet` API in the <a href='Injector-class.html'><code>Injector</code></a>.