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);10             _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, 0, 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, 0, 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。