同步/异步网络请求

字符串转为数据:[target dataUsingEncoding:];

数据转为字符串:[[NSString alloc]initWithData:encoding:];

响应状态:[NSHTTPURLResponse  localizedStringForStatusCode:];

异步post开子线程写

1.HTTP请求方法
GET请求
POST请求
这2种请求方法都要大写字母。
2.区别
GET：通常用于请求URL并得到资源
POST：用于提交数据到服务器
如GET：
http://www.baidu.com/img/123.jpg
http://www.baidu.com?name=123
3.URL连接方式
同步连接（软件安装）：同步（需要等待的状态），一个人做多件事，要完成1件才可以做第2件
异步连接（后台下载）：多处理（单件事多个人做），通过代理实现
总的来说：当请求的数据量小时，同步连接是不错的选择，缺点：UI会“冻结”。异步连接适用于大数据，UI不“冻结”。
4.NSString、NSData、NSArray、UImage等类都有从URL初始化数据的方法，这个方法便是系统封装好的GET请求的同步连接方式。

5.创建一个GET同步连接
step1.创建URL对象,指定路径
step2.创建NSURLRequest对象，设置请求方法，默认GET
step3.创建NSURLConnect对象，发送同步连接（核心步骤）
step4.接收数据
6.创建一个POST同步连接
step2：创建NSMutableURLRequest对象，设置为POST连接方式
7.GET异步连接
step1.创建URL对象,指定路径
step2.创建NSURLRequest对象，设置请求方法，默认GET
step3:创建NSURLConnection对象，并设置代理，发送异步连接
step4.代理方法中接收数据
8.POST异步连接
step2：创建NSMutableURLRequest对象，设置为POST连接方式

GET同步

 // 1.创建URL对象
    NSURL * url = [NSURL URLWithString:@"http://192.168.1.5:8080/Jersey/rest/contacts"];
    // 2.创建 NSURLRequest 对象
    NSURLRequest * request = [NSURLRequest requestWithURL:url
                                              cachePolicy:NSURLRequestReloadIgnoringCacheData // 忽略缓存
                                          timeoutInterval:10.0f];
    
    // 3.创建 NSURLConnection 对象，发送同步请求
    // 设置回应和错误的指针变量
    NSHTTPURLResponse * response = nil;
    NSError * error = nil;
    // 发起同步链接
    NSData * data = [NSURLConnection sendSynchronousRequest:request//同步会卡在这里
                                          returningResponse:&response
                                                      error:&error];
    
    
    // 4.接收数据
    // 打印回应和错误信息
    NSLog(@"response = %@",[NSHTTPURLResponse localizedStringForStatusCode:[response statusCode]]);
    NSLog(@"error = %@",[error localizedRecoveryOptions]);
    // 打印字符串信息
    NSString * str = [[NSString alloc] initWithData:data
                                           encoding:NSUTF8StringEncoding];
    
    if (response.statusCode == 200)
    {
        NSLog(@"str = %@",str);
    }
    //NSLog(@"str = %@",str);
    // 打印请求方式
    NSLog(@"request method = %@",[request HTTPMethod]);

POST同步

  // 1
    NSURL * url2 = [NSURL URLWithString:@"http://192.168.1.5:8080/Jersey/rest/contacts/addContact"];
    // 2
    NSMutableURLRequest * req = [NSMutableURLRequest requestWithURL:url2
                                                        cachePolicy:NSURLRequestReloadIgnoringCacheData
                                                    timeoutInterval:10.0f];
    // 3
    NSString * string = @"<contact><id>3007</id><name>Song</name></contact>";
    NSData * postData = [string dataUsingEncoding:4 allowLossyConversion:YES];
    NSString * len = [NSString stringWithFormat:@"%d",postData.length];
    // 设置请求方式
    [req setHTTPBody:postData];
    [req setHTTPMethod:@"POST"];
    [req setValue:@"application/xml" forHTTPHeaderField:@"Content-Type"];
    [req setValue:len forHTTPHeaderField:@"Content-Length"];
    // 4
    NSError * err;
    NSURLResponse * resp;
    NSData *urlData = [NSURLConnection sendSynchronousRequest:req
                                            returningResponse:&resp
                                                        error:&err];
    
    // 5
    NSString * responseStr = [[NSString alloc] initWithData:urlData
                                                   encoding:NSUTF8StringEncoding];
    
    NSLog(@"request method = %@",[req HTTPMethod]);
    NSLog(@"len = %@",len);
    NSLog(@"responseStr = %@",responseStr);

 异步

AppDelegate.h

#import <UIKit/UIKit.h>

@interface AppDelegate : UIResponder <UIApplicationDelegate,NSURLConnectionDataDelegate>
{
    NSMutableData *_mData;
}
@property (strong, nonatomic) UIWindow *window;

@end

AppDelegate.m

GET异步

NSString *str = @"http://192.168.1.5:8080/Jersey/rest/contacts";
    //1
    NSURL *url = [NSURL URLWithString:str];
    NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:10.0f];
    //
    [NSURLConnection connectionWithRequest:request delegate:self];

POST异步

NSString *str = @"http://192.168.1.5:8080/Jersey/rest/contacts/addContact";
    NSURL *url = [NSURL URLWithString:str];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:10.0f];
    //
    NSString *string = @"<contact><id>3007</id><name>Song</name></contact>";
    
    NSData *postData = [string dataUsingEncoding:4
                            allowLossyConversion:YES];//api上说没法识别时,是否支持转换为同一编码,也就是否允许失真
    
    NSString *len = [NSString stringWithFormat:@"%d",postData.length];//内容的字节长度
    
    
    [request setValue:@"application/xml" forHTTPHeaderField:@"Content-Type"];
    [request setHTTPBody:postData];
    [request setHTTPMethod:@"POST"];
    
    
    [NSURLConnection connectionWithRequest:request delegate:self];//?该返回值有什么用,为什么不用[NSURLConnection sendAsynchronousRequest:];
    
    NSLog(@"request method = %@",[request HTTPMethod]);
    NSLog(@"len = %@",len);

重写代理方法,系统自动调用

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSLog(@"%s",__func__);//服务器响应就会执行这个方法
    _mData = [[NSMutableData alloc]init];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    NSLog(@"%s",__func__);//当开始接受到数据的时候,数据量大的时候执行多次
    [_mData appendData:data];//将多个数据添加到可变data中
    //算进度
}

-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSLog(@"%s",__func__);//数据接受完后
    NSString *str = [[NSString alloc]initWithData:_mData encoding:4];
    NSLog(@"str = %@",str);
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    NSLog(@"%s",__func__);//连接接受失败
}
//文件读写
    //写文件
    NSString *path1 = @"/Users/yf02/Desktop/Oc_12/123.txt";
    
    
    NSString *content = @"i am a ios developer";
    
    NSError *error = nil;
    BOOL s = [content writeToFile:path1//写到的位置,默认覆盖,没追加
                       atomically:YES//Yes 先写到缓存,再从缓存写入文件
                         encoding:NSUTF8StringEncoding
                            error:&error];//指针的指针,有2个返回值
    if (!s)
    {
        NSLog(@"error:%@",[error localizedFailureReason]);
        exit(-1);
    }
    
    //读文件(url可以是网络路径[NSURL URLWithString:],也可以本地路径)
    NSURL *url = [NSURL fileURLWithPath:path1];
    NSString *u = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&error];
    NSLog(@"%@",u);
    
    
    
    //NSData主要存二进制数据(系统常用二进制文件)
    NSData *data = [NSData dataWithContentsOfFile:path1];
    NSLog(@"%@",data);
    NSString *dataCoutent = [[NSString alloc]initWithData:data encoding:4];
    NSLog(@"%@",dataCoutent);
    //写
    [data writeToFile:path1 atomically:YES];//不用编码,比字符串更安全更快速
    
    
    
    //NSFileManger对目录操作(单例)
    NSFileManager *fm = [NSFileManager defaultManager];
    [fm createDirectoryAtPath:@"/Users/yf02/Desktop/Oc_12/abc/123"
  withIntermediateDirectories:YES//中间目录
                   attributes:nil//nil默认为可以读可写
                        error:nil];
    
    [fm createFileAtPath:@"/Users/yf02/Desktop/Oc_12/abc/123/helloworld.txt"
                contents:data
              attributes:nil];
    
    [fm moveItemAtPath:@"/Users/yf02/Desktop/Oc_12/abc/123/helloworld.txt"
                toPath:@"/Users/yf02/Desktop/Oc_12/abc/helloworld.txt"
                 error:nil];
    
    
    
    //包(单例)
    NSBundle *mainBundle = [NSBundle mainBundle];
    NSString *mainBundlePath = [mainBundle pathForResource:@"helloworld" ofType:@"txt"];//要先关联好文件
    NSLog(@"mainBundlePath:%@",mainBundlePath);
    NSString *BundleContent= [NSString stringWithContentsOfFile:mainBundlePath encoding:4 error:nil];
    NSLog(@"BundleContent = %@",BundleContent);
    //NSBundle不能写入内容
    NSString *string1 = @"abc";
    BOOL return1 = [string1 writeToFile:mainBundlePath
                             atomically:YES
                               encoding:4
                                  error:nil];
    NSLog(@"return1 = %d",return1);
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原文地址：https://www.cnblogs.com/huen/p/3546475.html