iOS网络编程--NSConnection的同步连接与异步连接

 //
 //  ZFViewController.m
 //  0628-表单验证
 //
 //  Created by zfan on 14-6-28.
 //  Copyright (c) 2014年 zfan. All rights reserved.
 //

 #import "ZFViewController.h"
 #import "MBProgressHUD+MJ.h"

 @interface ZFViewController ()

 @property (weak, nonatomic) IBOutlet UITextField *userNameTextField;
 @property (weak, nonatomic) IBOutlet UITextField *passWordTextField;

 @end

 @implementation ZFViewController

 - (void)viewDidLoad
 {
     [super viewDidLoad];
 }

 - (IBAction)login:(id)sender
 {
     //验证账号和密码是否合法
     if (self.userNameTextField.text.length == )
     {
         [MBProgressHUD showError:@"请输入账号"];
         return;
     }

     if (self.passWordTextField.text.length == )
     {
         [MBProgressHUD showError:@"请输入密码"];
         return;
     }

     //取出账号和密码
     NSString *userName = self.userNameTextField.text;
     NSString *password = self.passWordTextField.text;

     //生成URL
     NSString *urlPath = [NSString stringWithFormat:@"http://192.168.1.101:8080/ZFServer/login?username=%@&pwd=%@", userName, password];
     NSURL *url = [NSURL URLWithString:urlPath];

     //生成连接
     NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url];

     //建立连接并接收返回数据(同步执行)
 //    NSData *loginData = [NSURLConnection sendSynchronousRequest:urlRequest returningResponse:nil error:nil];

     //建立连接并接收返回数据(异步执行)
     NSOperationQueue *queue = [[NSOperationQueue alloc] init];
     [NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
         NSData *loginData = data;
         NSLog(@"%ld", (unsigned long)loginData.length);
     }];

     //打印返回的数据长度
     NSLog(@"%@", self.userNameTextField.text);
     NSLog(@"%@", self.passWordTextField.text);
 //    NSLog(@"%ld", (unsigned long)loginData.length);
 }

 @end

知识要点:

1>通过NSString类方法拼接字符串,生成完整的URL路径;

2>通过NSURLRequest的类方法,利用URL建立一个NSURLRequest连接实例;

3>通过NSConnection的类方法建立连接并接受返回数据,可通过同步方式和异步方式实现:

　　3.1>同步方式

[NSURLConnection sendSynchronousRequest:urlRequest returningResponse:nil error:nil];

　　此方法不会新建线程,返回值为NSData,由于未新建线程,因此在该方法未完成前,线程不会继续向下运行,容易造成卡死;

　　3.2>异步方式

NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
　　NSData *loginData = data;
　　NSLog(@"%ld", (unsigned long)loginData.length);
}];

　　此方法会建立一个新的线程用于接受网络端返回数据,返回值为void,当数据接受完毕后会执行block中的语句;