使用RX方式模拟DoubanFm的登陆

WP7下的Get Post都是异步的

关于RX

http://www.cnblogs.com/yangecnu/archive/2012/11/03/Introducting_ReactiveExtensions.html

我初步理解的Rx,是观察者模式的一种实现

Url很简单，先来看看URL

• URL: http://www.douban.com/j/app/login

• Method: POST

• Arguments:

  • app_name: radio_desktop_win

  • version: 100

  • email: 用户帐号

  • password: 明文密码

• Header: Content-Type: application/x-www-form-urlencoded

• Response ( application/json )

在WP7下的Post过程大致如下（Get过程相对简单，只需要2步）:

第一步：

     public void PostMethod(string Url,string Postdata)
         {

             HttpWebRequest request;
             request = (HttpWebRequest)WebRequest.Create(new Uri(Url));
             request.Method = "POST";
             request.ContentType = "application/x-www-form-urlencoded";
             request.BeginGetRequestStream(new AsyncCallback(RequestCallback), request);             _postdata = Postdata;
         }

第二步：

    private void RequestCallback(IAsyncResult asyncResult)
         {
            HttpWebRequest request = (HttpWebRequest)asyncResult.AsyncState;
             UTF8Encoding encoding = new UTF8Encoding();
             Stream _body = request.EndGetRequestStream(asyncResult);
             byte[] formBytes = encoding.GetBytes(_postdata);//这是通过post方式传的
             _body.Write(formBytes, , formBytes.Length);
             _body.Close();
             request.BeginGetResponse(new AsyncCallback(ResponseCallback), request);

          }

第三步：

      private void ResponseCallback(IAsyncResult asyncResult)
         {
             HttpWebRequest request = (HttpWebRequest)asyncResult.AsyncState;

                     WebResponse httpwebresponse = request.EndGetResponse(asyncResult);
                     Stream stream=   httpwebresponse.GetResponseStream();
                     StreamReader reader = new StreamReader(stream);
                     string result=reader.ReadToEnd();

             // Deployment.Current.Dispatcher.BeginInvoke(_postret, result);

         }

刚学习了Rx，想看看如果用Rx应该怎么做

先来回顾下Rx 如下

public interface IObservable<T>  {  IDisposable Subscribe(IObserver<T> observer); }

    public interface IObserver<T>
     {
         void OnCompleted();
         void OnError(Exception exception);
         void OnNext(T value);
     }

在我的System.Reactive.Linq的Observable静态类下，定义了了IObservable<T>的很多扩展方法，

    public static IObservable<TResult> Select<TSource, TResult>(this IObservable<TSource> source, Func<TSource, TResult> selector)

  public static IObservable<TResult> SelectMany<TSource, TResult>(this IObservable<TSource> source, Func<TSource, IEnumerable<TResult>> selector)

这些扩展方法反映了我们可以像Linq一样获得一个IObservable<T>

下面是获得一个IObservable<T>的最简单的方法

  public static IObservable<TResult> Return<TResult>(TResult value)

用这个方法得到的IObservable<T>后就可以注册了，在我的System.Reactive.Core.dll，System命名空间下的ObservableExtensions静态类扩展了IObservable<T>的注册方式：

  public static IDisposable Subscribe<T>(this IObservable<T> source, Action<T> onNext)
         {
             if (source == null)
             {
                 throw new ArgumentNullException("source");
             }
             if (onNext == null)
             {
                 throw new ArgumentNullException("onNext");
             }
             return source.Subscribe(new AnonymousObserver<T>(onNext, Stubs.Throw, Stubs.Nop));
         }

具体实现我们不具体去关注，但是我们知道在11行，是New了一个匿名的观察者Observer了。

接下来看看FromAsyncPattern

  public static Func<IObservable<TResult>> FromAsyncPattern<TResult>(Func<AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)

这是个静态方法，返回一个返回值类型为IObservable<TResult>,无实参,的委托

先回顾用Rx实现的一个Get方法：

   public LoginTest()
         {

          var func=  Observable.FromAsyncPattern<HttpWebRequest,HttpWebResponse>(Webrequest,WebResponse);
          HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create("http://www.baidu.com");

         var observable= func(request);
         observable.Subscribe(
             (result) =>
             {
                 var stream = result.GetResponseStream();
                 var sr = new StreamReader(stream);
                 var baiduhttphtml = sr.ReadToEnd();
             });

         }

         IAsyncResult Webrequest(HttpWebRequest request,AsyncCallback callbcak,object ob)
         {
             return request.BeginGetResponse(callbcak, request);
         }
         HttpWebResponse WebResponse(IAsyncResult result)
         {
             var request = result.AsyncState as HttpWebRequest;
           return (HttpWebResponse)request.EndGetResponse(result);
         }

这样的Get方式看起来很简洁

昨晚敲了一下,Post方式如下：（回去后在VS2013上用RX，发现他提示我最好用await，Task等新特性来做异步，今晚回去试试，实验室是VS2010）

  class MyHttpRequest
         {
             string PostData;
             AsyncCallback save;//用于中间传递
             public  IObservable<string> PostMethod(string URL, string PostData)
             {
                 this.PostData = PostData;
                 var func = Observable.FromAsyncPattern<HttpWebRequest,string>(Webrequest, ResponseCallback);//直接返回string
                 HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(URL);
                 request.Method = "POST";
                 request.ContentType = "application/x-www-form-urlencoded";
               return  func(request);

             }
             IAsyncResult Webrequest(HttpWebRequest request, AsyncCallback callbcak, object ob)
             {
                 save = callbcak;//保存CallBack
                 return request.BeginGetRequestStream(act, request);
             }
             void act(IAsyncResult asyncResult)
             {
                 HttpWebRequest request = (HttpWebRequest)asyncResult.AsyncState;
                 UTF8Encoding encoding = new UTF8Encoding();
                 Stream _body = request.EndGetRequestStream(asyncResult);
                 byte[] formBytes = encoding.GetBytes(this.PostData);//这是通过post方式传的
                 _body.Write(formBytes, , formBytes.Length);
                 _body.Close();
                 request.BeginGetResponse(save, request);//用保存的CallBack

             }
             string ResponseCallback(IAsyncResult asyncResult)
             {
                 HttpWebRequest request = (HttpWebRequest)asyncResult.AsyncState;
                 WebResponse httpwebresponse = request.EndGetResponse(asyncResult);
                 Stream stream = httpwebresponse.GetResponseStream();
                 StreamReader reader = new StreamReader(stream);
                 return reader.ReadToEnd();
             }
         }

好了，现在很清楚了，来试试效果

     public LoginTest()
         {
             //发出一个消息 跟MVVMLight Messenger有点像
         var observable=    new MyHttpRequest().PostMethod("http://www.douban.com/j/app/login", "app_name=radio_desktop_win&version=100&email=327442095@qq.com&password=");

             //直接在这里订阅一个匿名接收者
         observable.Subscribe((result) =>
             {
                 Debug.WriteLine(result);
             });
         Debug.WriteLine("我比你先返回，哈哈");
         }

~OK。

可以使用这个方式做我的FM登陆了。