app.controller('myFactoryCtrl', function($scope, myFactory){
  $scope.artist = myFactory.getArtis();
});
app.factory('myFactory', function(){
  var _artist = '';
  var service = {};

  service.getArtist = function(){
    return _artist;
  }
  return service;
});

app.controller('myFactoryCtrl', function($scope, myService){
  $scope.artist = myService.getArtis();
});
app.service('myService', function(){
  var _artist ='';
  this.getArtist = function(){
    return _artist;
  }
});

app.controller('myProviderCtrl', function($scope, myProvider){
  $scope.artist = myProvider.getArtist();
  $scope.data.thingFromConfig = myProvider.thingOnConfig;
});
app.provider('myProvider', function(){
  this._artist = '';
  this.thingFromConfig = '';

  this.$get = function(){
    var that = this;
    return {
       getArtist: function(){
         return that._artist;
       },
       thingOnConfig: that.thingFromConfig
    }
  }
});
app.config(function(myProviderProvider){
  myProviderProvider.thingFromConfig = 'This was set in config()';
});

$provide.value('myValue', 10);
$provide.constant('myConstant', 10);
/*


二者的区别：
1. value可以被修改，constant一旦声明就无法修改
2. value不可以在config中注入，constant可以。
*/

app.provider('myDate', { 
  $get: function() { 
   return new Date(); 
  }
});
//可以写成
app.factory('myDate', function(){ 
 return new Date();
});
//可以写成
app.service('myDate', Date);