本文以新浪微博的Oauth认证为例子进行Post请求的演示

下面直接上代码：

#import "ViewController.h"
#import "AFNetworking.h"

@interface ViewController ()<UIWebViewDelegate,NSURLConnectionDelegate>

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    NSString* urlStr = @"https://api.weibo.com/oauth2/authorize?client_id=3145625561&redirect_uri=http://www.baidu.com&display=mobile";
    
    //将字符串转化为URL
    NSURL* url = [NSURL URLWithString:urlStr];
NSMutableURLRequest* request = [[NSMutableURLRequest alloc] initWithURL:url];
    UIWebView *webView = [[UIWebView alloc] initWithFrame:self.view.frame];
    [webView loadRequest:request];
    webView.delegate = self;
    [self.view addSubview:webView];
}

- (BOOL) webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType
{
    
    NSURL* resultStr = [request URL];
    NSString* tempStr = [resultStr absoluteString];
    NSLog(@"%@",resultStr);
    //判断字符串中是否包含code=
    NSRange range =  [tempStr rangeOfString:@"code="];
    //如果不包含会返回为真，因此此处取反，就是说不为空的时候会为假，取反之后为真
    if ( !(range.location == NSNotFound)) {
        //absoluteString作用是将NSURL类型转化为NSString
        NSString* tempStr = [resultStr absoluteString];
        //componentsSeparatedByString
        NSArray* codeArr =  [tempStr componentsSeparatedByString:@"="];
        
        
        NSLog(@"%@",codeArr);
        NSString* code = [codeArr objectAtIndex:1];
        NSLog(@"code = %@",code);
        //之后在此处下一行添加调用获取access_token值的方法即httpRequest:(NSString*)codeStr
        [self httpPostRequest:code];
    }
    
    return YES;
}

- (void)httpPostRequest:(NSString *)code
{
    /****本文主要讲解内容*****/
    AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
    manager.responseSerializer.acceptableContentTypes = [NSSet setWithObject:@"text/plain"];
    NSDictionary *parameters = @{@"client_id":@"3145625561",
                                 @"client_secret":@"0a61cc8a017fa8ba6c98532fefa3c29c",
                                 @"grant_type":@"authorization_code",
                                 @"code":code,
                                 @"redirect_uri":@"http://www.baidu.com"};
    
    [manager POST:@"https://api.weibo.com/oauth2/access_token?" parameters:parameters success:^(AFHTTPRequestOperation *operation, id responseObject) {
        
        NSLog(@"Success:%@" , responseObject);
        
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        NSLog(@"%@",error);
        
    }];
    
}

特别提示一下：

manager.responseSerializer.acceptableContentTypes = [NSSetsetWithObject:@"text/plain"];这里如果返回是JSON的话要用     text/plain    不然会报错。

代码例子：http://pan.baidu.com/s/1bn0FieN

AFNetworking2.0后 进行Post请求