前一章用MKNetworkit和Express模拟了登陆验证的功能，但是在实际应用中会出现一个问题，就是MKNetworkit并不支持同步，也就是说在登陆验证的时候，可能服务器数据还未返回，就已经开始了下一步操作，比如说跳转到下个界面。

比较简单地解决方法就是用Rest web Service基础的同步get,post方法实现登陆验证。

直接上代码：

-(void)loginpost:(NSString*)user pwd:(NSString*)password{
    [GMDCircleLoader setOnView:self.view withTitle:@"Loading..." animated:YES];//一个第三方的活动指示器
//    [self.act startAnimating];
//    [self.view addSubview:self.act];

    NSURL* host = [NSURL URLWithString:@"http://127.0.0.1:3000/login?"];
    NSString* path = [[NSString alloc]initWithFormat:@"user=%@&password=%@",user,password];
    NSData* pathdata = [path dataUsingEncoding:NSUTF8StringEncoding];//post内容序列化

    NSMutableURLRequest* req = [[NSMutableURLRequest alloc]initWithURL:host cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10];
    [req setHTTPMethod:@"POST"];
    [req setHTTPBody:pathdata];
    NSError* e=nil;

    NSData* recivedata = [NSURLConnection   
           sendSynchronousRequest:req
           returningResponse:nil error:&e];//同步请求
    if(e){//连接服务器错误
    [NSTimer scheduledTimerWithTimeInterval:3.0 
    target:self selector:@selector(connectfailed:) 
    userInfo:[e localizedDescription] 
    repeats:NO];
        return;
    }

    //成功返回数据
    if(recivedata){
        NSError* er = nil;
        NSDictionary* dict = [NSJSONSerialization JSONObjectWithData:recivedata options:NSJSONReadingAllowFragments error:&er];
        if(!er){
            NSString* rescode = [dict valueForKey:@"resultcode"];
            if([rescode isEqualToString:@"true"]){
                [NSTimer scheduledTimerWithTimeInterval:3.0 target:self selector:@selector(logined) userInfo:nil repeats:NO];
            }else{
                [NSTimer scheduledTimerWithTimeInterval:3.0 target:self selector:@selector(loginedfailed) userInfo:nil repeats:NO];


            }

        }

    }   
}

登陆验证的时候会有三种情况，一种根本连不上数据库，一种用户名或者密码错误，一种登陆成功。这里加上活动指示器，是为了防止和服务器通信时间过长导致的主界面“假死”。

//链接失败
-(void)connectfailed:(NSTimer*)timer{
    [GMDCircleLoader hideFromView:self.view animated:YES];
//    [self.act stopAnimating];
//    [self.act removeFromSuperview];
    NSLog(@"conenctd failed");
    UIAlertView* alter = [[UIAlertView alloc]initWithTitle:@"错误" message:[timer userInfo] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles: nil];
    [alter show];
}
//登陆成功
-(void)logined{
    [GMDCircleLoader hideFromView:self.view animated:YES];
//    [self.act stopAnimating];
//    [self.act removeFromSuperview];
    NSLog(@"login success!");
    [self performSegueWithIdentifier:@"showdetail" sender:self];
}

//用户名或密码错误
-(void)loginedfailed{
    [GMDCircleLoader hideFromView:self.view animated:YES];
//    [self.act stopAnimating];
//    [self.act removeFromSuperview];
     NSLog(@"login failed!");
    UIAlertView* alter = [[UIAlertView alloc]initWithTitle:@"登陆失败" message:@"用户名或密码错误" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alter show];

}

这里用了个第三方的活动指示器，具体链接：
https://github.com/gabemdev/GMDCircleLoader
注释掉的都是自带的UIActivityIndicatorView，使用方法也很简单，直接在
viewDidLoad中初始化：

self.size = self.view.frame.size;
self.act = [[UIActivityIndicatorView alloc]initWithFrame:CGRectMake(self.size.width/2-50, self.size.height/3, 100, 50)];
self.act.activityIndicatorViewStyle=UIActivityIndicatorViewStyleGray;//指示器类型
 //设置活动指示器的颜色
 elf.act.color=[UIColor redColor];
 //hidesWhenStopped默认为YES，就是只有在指示器运行的时候才显示
 self.act.hidesWhenStopped=YES;

项目文件：
https://github.com/tyrantkemp/login.git