非单服务在角 [英] Non-Singleton Services in Angular

问题描述

角清楚的说明文件中指出，服务是单身：

 角服务是单身
 

直觉相反， module.factory 也返回一个Singleton实例。

由于有大量的应用案例非单服务，什么是实现工厂方法返回一个服务的情况下，最好的方式，让每一次的 ExampleService 依赖声明，它是由 ExampleService ？

解决方案

我不认为我们应该永远有一个工厂返回一个新能功能，因为这开始打破依赖注入和图书馆的行为笨拙，特别是对第三方。总之，我不知道有任何合法的用例非单服务队。

有一个更好的方式来完成同样的事情是用工厂作为API返回对象的集合与连接到他们的getter和setter方法​​。这里是显示使用这种服务的可能是如何工作的一些伪code：

.controller（'MainCtrl'，函数（$范围，widgetService）{
  $ scope.onSearchFormSubmission =功能（）{
    widgetService.findById（$ scope.searchById）。然后（功能（部件）{
      //这是一个返回的对象，完成了所有的getter / setter方法
      $ scope.widget =部件;
    }）;
  };  $ scope.onWidgetSave =功能（）{
    //这个方法仍然存在widget对象
    。$ scope.widget $保存（）;
  };
}）;


这仅仅是伪code用于查找由ID的小部件，然后能够保存到记录所做的更改。

下面是一些伪code的服务：

.factory（'widgetService'，函数（$ HTTP）{  功能的Widget（JSON）{
    angular.extend（这一点，JSON）;
  }  Widget.prototype = {
    $保存：功能（）{
      // TODO：带不相干的领域
      VAR scrubbedObject = // ...
      返回$ http.put（'/widgets/'+this.id，scrubbedObject）;
    }
  };  功能getWidgetById（ID）{
    返回HTTP $（'/部件/'+ ID）。然后（函数（JSON）{
      返回新控件（JSON）;
    }）;
  }
  //公共控件API
  返回{
    // ...
    findById：getWidgetById
    // ...
  };
}）;


虽然在这个例子中不包括在内，这类灵活的服务还可以轻松管理状态。

---

我没有时间，现在，但是，如果这将有助于我以后可以组成一个简单的Plunker证明。

Angular clearly states in its documentation that Services are Singletons:

Angular services are singletons

Counterintuitively, module.factory also returns a Singleton instance.

Given that there are plenty of use-cases for non-singleton services, what is the best way to implement the factory method to return instances of a Service, so that each time an ExampleService dependency is declared, it is satisfied by a different instance of ExampleService?

解决方案

I don't think we should ever have a factory return a newable function as this begins to break down dependency injection and the library will behave awkwardly, especially for third parties. In short, I am not sure there are any legitimate use cases for non-singleton sevices.

A better way to accomplish the same thing is to use the factory as an API to return a collection of objects with getter and setter methods attached to them. Here is some pseudo-code showing how using that kind of service might work:

.controller( 'MainCtrl', function ( $scope, widgetService ) {
  $scope.onSearchFormSubmission = function () {
    widgetService.findById( $scope.searchById ).then(function ( widget ) {
      // this is a returned object, complete with all the getter/setters
      $scope.widget = widget;
    });
  };

  $scope.onWidgetSave = function () {
    // this method persists the widget object
    $scope.widget.$save();
  };
});

This is just pseudo-code for looking up a widget by ID and then being able to save changes made to the record.

Here's some pseudo-code for the service:

.factory( 'widgetService', function ( $http ) {

  function Widget( json ) {
    angular.extend( this, json );
  }

  Widget.prototype = {
    $save: function () {
      // TODO: strip irrelevant fields
      var scrubbedObject = //...
      return $http.put( '/widgets/'+this.id, scrubbedObject );
    }
  };

  function getWidgetById ( id ) {
    return $http( '/widgets/'+id ).then(function ( json ) {
      return new Widget( json );
    });
  }


  // the public widget API
  return {
    // ...
    findById: getWidgetById
    // ...
  };
});

Though not included in this example, these kinds of flexible services could also easily manage state.

---

I don't have time right now, but if it will be helpful I can put together a simple Plunker later to demonstrate.

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