From 0c4fbfc8e237b83024c9d5c58123bf16d0b604b7 Mon Sep 17 00:00:00 2001
From: Pawel Kozlowski <pkozlowski.opensource@gmail.com>
Date: Sat, 21 Feb 2015 15:18:06 +0100
Subject: [PATCH] feat(di): introduce aliasing

Closes #710
Closes #747
---
 modules/angular2/docs/di/di.md            | 12 +++++++++++-
 modules/angular2/src/di/binding.js        |  9 +++++++++
 modules/angular2/test/di/injector_spec.js | 22 +++++++++++++++++++++-
 3 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/modules/angular2/docs/di/di.md b/modules/angular2/docs/di/di.md
index 88cd9c33ce..549762b57f 100644
--- a/modules/angular2/docs/di/di.md
+++ b/modules/angular2/docs/di/di.md
@@ -96,7 +96,7 @@ var car = child.get(Car); // uses the Car binding from the parent injector and E
 
 ## Bindings
 
-You can bind to a class, a value, or a factory
+You can bind to a class, a value, or a factory. It is also possible to alias existing bindings.
 
 ```
 var inj = new Injector([
@@ -128,6 +128,16 @@ var inj = new Injector([
 ]);
 ```
 
+If you want to alias an existing binding, you can do so using `toAlias`:
+
+```
+var inj = new Injector([
+	bind(Engine).toClass(Engine),
+	bind("engine!").toAlias(Engine)
+]);
+```
+which implies `inj.get(Engine) === inj.get("engine!")`.
+
 Note that tokens and factory functions are decoupled.
 
 ```
diff --git a/modules/angular2/src/di/binding.js b/modules/angular2/src/di/binding.js
index 690a8a192d..c89af011e6 100644
--- a/modules/angular2/src/di/binding.js
+++ b/modules/angular2/src/di/binding.js
@@ -60,6 +60,15 @@ export class BindingBuilder {
     );
   }
 
+  toAlias(aliasToken):Binding {
+    return new Binding(
+      Key.get(this.token),
+      (aliasInstance) => aliasInstance,
+      [new Dependency(Key.get(aliasToken), false, false, [])],
+      false
+    );
+  }
+
   toFactory(factoryFunction:Function, dependencies:List = null):Binding {
     return new Binding(
       Key.get(this.token),
diff --git a/modules/angular2/test/di/injector_spec.js b/modules/angular2/test/di/injector_spec.js
index ee2ef4bfc8..03c7de1edb 100644
--- a/modules/angular2/test/di/injector_spec.js
+++ b/modules/angular2/test/di/injector_spec.js
@@ -128,6 +128,26 @@ export function main() {
       expect(car.engine).toBeAnInstanceOf(Engine);
     });
 
+    it('should bind to an alias', function() {
+      var injector = new Injector([
+        Engine,
+        bind(SportsCar).toClass(SportsCar),
+        bind(Car).toAlias(SportsCar)
+      ]);
+
+      var car = injector.get(Car);
+      var sportsCar = injector.get(SportsCar);
+      expect(car).toBeAnInstanceOf(SportsCar);
+      expect(car).toBe(sportsCar);
+    });
+
+    it('should throw when the aliased binding does not exist', function () {
+      var injector = new Injector([
+        bind('car').toAlias(SportsCar)
+      ]);
+      expect(() => injector.get('car')).toThrowError('No provider for SportsCar! (car -> SportsCar)');
+    });
+
     it('should support overriding factory dependencies', function () {
       var injector = new Injector([
         Engine,
@@ -324,4 +344,4 @@ export function main() {
       });
     });
   });
-}
\ No newline at end of file
+}