網絡請求包括GET.POST兩種方式，其步驟為：1>獲取URL。 2>獲取請求。 3>創建鏈接。 4>返回數據（代理）。

1>獲取URL。

NSString *urlStr=@"http://api.zbw.vc/api/vip/GetPhonePadTagMsg";
//當參數為中文時，用UTF8編碼
//urlStr=[urlStr stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSURL *url=[NSURL URLWithString:urlStr];

2>獲取請求。

NSURLRequest *request=[NSURLRequest requestWithURL:url];

默認get方法的參數只需要URL拼接。

當創建post方法的時候，對request進行如下操作

NSString *dataStr=[NSString stringWithFormat:@"UserName=%@&LoginPwd=%@",self.QQField.text,self.pwdField.text];
NSData *data=[dataStr dataUsingEncoding:NSUTF8StringEncoding];
[request setHTTPBody:data];
[request setHTTPMethod:@"POST"];
[request setTimeoutInterval:5.0];

3>創建鏈接。

此時，創建的 代理為本類，所以該類必須繼承協議

NSURLConnection *conn=[NSURLConnection connectionWithRequest:request delegate:self];

4>返回數據（代理）。實現代理必須實現如下方法

//網絡返回數據開始
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
//重復調用，返回數據處理
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
//返回數據結束
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
//發生錯誤處理方法
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error

IOS提供另一種方法實現數據回傳

1.同步>>

NSData *data=[NSURLConnection sendSynchronousRequest:request returningResponse:&resp error:&error];

2.異步>>

[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(block)];

具體代碼如下：

#import "CSZViewController.h"

@interface CSZViewController ()

@property (nonatomic,strong) NSMutableData *mutableData;

@end

@implementation CSZViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

}


- (NSURLRequest *)getRequest {
    NSString *urlStr=@"http://api.zbw.vc/api/vip/GetPhonePadTagMsg";
    //當參數為中文時，用UTF8編碼
    //urlStr=[urlStr stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSURL *url=[NSURL URLWithString:urlStr];
    
    NSURLRequest *request=[NSURLRequest requestWithURL:url];
    return request;
}

- (IBAction)getLogin {
    
    NSURLRequest *request = [self getRequest];
    NSURLConnection *conn=[NSURLConnection connectionWithRequest:request delegate:self];
    [conn start];
}

- (NSMutableURLRequest *)getAsyncRequest {
    NSString *urlStr=@"http://api.zbw.vc/api/Vip/PostUserInfo";
    NSURL *url=[NSURL URLWithString:urlStr];
    NSMutableURLRequest *request=[NSMutableURLRequest requestWithURL:url];
    
    NSString *dataStr=[NSString stringWithFormat:@"UserName=%@&LoginPwd=%@",self.QQField.text,self.pwdField.text];
    
    NSData *data=[dataStr dataUsingEncoding:NSUTF8StringEncoding];
    
    [request setHTTPBody:data];
    [request setHTTPMethod:@"POST"];
    [request setTimeoutInterval:5.0];
    return request;
}

- (IBAction)postLogin {
    
    [UIApplication sharedApplication].networkActivityIndicatorVisible=YES;
    
    NSMutableURLRequest *request = [self getAsyncRequest];
    NSURLConnection *conn=[NSURLConnection connectionWithRequest:request delegate:self];
    [conn start];
}

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSLog(@"%@",@"網絡返回數據開始");
}

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    if (_mutableData==nil) {
        _mutableData=[NSMutableData data];
    }
    [_mutableData appendData:data];
}

-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    _mutableData=nil;
}

-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSString *str=[[NSString alloc] initWithData:_mutableData encoding:NSUTF8StringEncoding];
    NSLog(@"%@",str);
    
    if (_mutableData!=nil) {
        _mutableData=nil;
    }
    [UIApplication sharedApplication].networkActivityIndicatorVisible=NO;
}

- (IBAction)clickSync {
    NSURLRequest *request = [self getRequest];
    NSURLResponse *resp=nil;
    NSError *error=nil;
    NSData *data=[NSURLConnection sendSynchronousRequest:request returningResponse:&resp error:&error];
    if (error!=nil) {
        NSLog(@"%@",error.localizedDescription);
        return;
    }
    
    if (data!=nil) {
        //解碼
        NSString *respStr=[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        NSLog(@"%@",respStr);
    }
    else
    {
        NSLog(@"獲取不到網絡數據");
    }
    
}

- (IBAction)clickAsync {
    NSURLRequest *request = [self getAsyncRequest];
    
    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
        if (connectionError!=nil) {
            NSLog(@"%@",connectionError.localizedDescription);
        }else if (response!=nil) {
            //解碼
            NSString *res=[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
            NSLog(@"%@",res);
        }else{
            NSLog(@"獲取不到網絡數據");
        }
    }];
    
    
}

@end