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 == 0)
    {
        [MBProgressHUD showError:@"请输入账号"];
        return;
    }
    
    if (self.passWordTextField.text.length == 0)
    {
        [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;