angularjs Service vs provider vs factory

稍後翻譯。

Services

Syntax: module.service( 'serviceName', function ); 
Result: When declaring serviceName as an injectable argument you will be provided with an instance of the function. In other words new FunctionYouPassedToService().

Factories

Syntax: module.factory( 'factoryName', function ); 
Result: When declaring factoryName as an injectable argument you will be provided with the value that is returned by invoking the function reference passed to module.factory.

Providers

Syntax: module.provider( 'providerName', function ); 
Result: When declaring providerName as an injectable argument you will be provided with ProviderFunction().$get(). The constructor function is instantiated before the $get method is called - ProviderFunction is the function reference passed to module.provider.

Providers have the advantage that they can be configured during the module configuration phase.

See here for the provided code: http://jsbin.com/ohamub/1/edit

Here's a great further explanation by Misko:

provide.value('a', 123);function Controller(a) {
  expect(a).toEqual(123);}

In this case the injector simply returns the value as is. But what if you want to compute the value? Then use a factory

provide.factory('b', function(a) {
  return a*2;});function Controller(b) {
  expect(b).toEqual(246);}

So factory is a function which is responsible for creating the value. Notice that the factory function can ask for other dependencies.

But what if you want to be more OO and have a class called Greeter?

function Greeter(a) {
  this.greet = function() {
    return 'Hello ' + a;
  }}

Then to instantiate you would have to write

provide.factory('greeter', function(a) {
  return new Greeter(a);});

Then we could ask for 'greeter' in controller like this

function Controller(greeter) {
  expect(greeter instanceof Greeter).toBe(true);
  expect(greeter.greet()).toEqual('Hello 123');}

But that is way too wordy. A shorter way to write this would be provider.service('greeter', Greeter);

But what if we wanted to configure the Greeter class before the injection? Then we could write

provide.provider('greeter2', function() {
  var salutation = 'Hello';
  this.setSalutation = function(s) {
    salutation = s;
  }

  function Greeter(a) {
    this.greet = function() {
      return salutation + ' ' + a;
    }
  }

  this.$get = function(a) {
    return new Greeter(a);
  };});

We can then do this:

angular.module('abc', []).config(function(greeter2Provider) {
  greeter2Provider.setSalutation('Halo');});function Controller(greeter2) {
  expect(greeter2.greet()).toEqual('Halo 123');}

As a side note, service, factory, and value are all derived from provider.

provider.service = function(name, Class) {
  provider.provide(name, function() {
    this.$get = function($injector) {
      return $injector.instantiate(Class);
    };
  });}provider.factory = function(name, factory) {
  provider.provide(name, function() {
    this.$get = function($injector) {
      return $injector.invoke(factory);
    };
  });}provider.value = function(name, value) {
  provider.factory(name, function() {
    return value;
  });};

參考：http://stackoverflow.com/questions/15666048/service-vs-provider-vs-factory