四种方法解析JSON数据

（1）使用TouchJSon解析方法：（需导入包：#import "TouchJson/JSON/CJSONDeserializer.h"）

 //使用TouchJson来解析北京的天气
 - (IBAction)btnPressTouchJson:(id)sender {
     //获取API接口
     NSURL *url = [NSURL URLWithString:@"http://m.weather.com.cn/data/101010100.html"];
     //定义一个NSError对象，用于捕获错误信息
     NSError *error;
     NSString *jsonString = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&error];
     NSLog(@"jsonString--->%@",jsonString);
     //将解析得到的内容存放字典中，编码格式为UTF8，防止取值的时候发生乱码
     NSDictionary *rootDic = [[CJSONDeserializer deserializer] deserialize:[jsonString dataUsingEncoding:NSUTF8StringEncoding] error:&error];
     //因为返回的Json文件有两层，去第二层内容放到字典中去
     NSDictionary *weatherInfo = [rootDic objectForKey:@"weatherinfo"];
     NSLog(@"weatherInfo--->%@",weatherInfo);
     //取值打印
     txtView.text = [NSString stringWithFormat:@"今天是 %@  %@  %@  的天气状况是：%@  %@ ",[weatherInfo objectForKey:@"date_y"]
                   ,[weatherInfo objectForKey:@"week"],[weatherInfo objectForKey:@"city"],[weatherInfo objectForKey:@"weather1"]
                   ,[weatherInfo objectForKey:@"temp1"]];
 }

（2）使用SBJson解析方法：（需导入包：#import "SBJson/SBJson.h"）

 //使用SBJson解析南阳的天气
 - (IBAction)btnPressSBJson:(id)sender {
     NSURL *url = [NSURL URLWithString:@"http://m.weather.com.cn/data/101180701.html"];
     NSError *error = nil;
     NSString *jsonString = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&error];
     SBJsonParser *parser = [[SBJsonParser alloc] init];
     
     NSDictionary *rootDic = [parser objectWithString:jsonString error:&error];
     NSDictionary *weatherInfo = [rootDic objectForKey:@"weatherinfo"];
     txtView.text = [NSString stringWithFormat:@"今天是 %@  %@  %@  的天气状况是：%@  %@ ",[weatherInfo objectForKey:@"date_y"]
                   ,[weatherInfo objectForKey:@"week"],[weatherInfo objectForKey:@"city"],[weatherInfo objectForKey:@"weather1"]
                   ,[weatherInfo objectForKey:@"temp1"]];
 }

（3）使用IOS5自带解析类NSJSONSerialization方法解析：（无需导入包，IOS5支持，低版本IOS不支持）

 - (IBAction)btnPressIOS5Json:(id)sender {
     
     NSError *error;
     //加载一个NSURL对象
     NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://m.weather.com.cn/data/101180601.html"]];
     //将请求的url数据放到NSData对象中
     NSData *response = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
     //IOS5自带解析类NSJSONSerialization从response中解析出数据放到字典中
     NSDictionary *weatherDic = [NSJSONSerialization JSONObjectWithData:response options:NSJSONReadingMutableLeaves error:&error];
     NSDictionary *weatherInfo = [weatherDic objectForKey:@"weatherinfo"];
     txtView.text = [NSString stringWithFormat:@"今天是 %@  %@  %@  的天气状况是：%@  %@ ",[weatherInfo objectForKey:@"date_y"]
                   ,[weatherInfo objectForKey:@"week"],[weatherInfo objectForKey:@"city"],[weatherInfo objectForKey:@"weather1"]
                   ,[weatherInfo objectForKey:@"temp1"]];
     NSLog(@"weatherInfo字典里面的内容为--》%@", weatherDic );
 }

（4）使用JSONKit的解析方法：（需导入包：#import "JSONKit/JSONKit.h"）

 - (void)btnPressJsonKit:(id)sender {
     //如果json是“单层”的，即value都是字符串、数字，可以使用    objectFromJSONString
 NSString *json1 = @"{\"a\":123, \"b\":\"abc\"}";
 NSLog(@"json1:%@",json1);
 NSDictionary *data1 = [json1 objectFromJSONString];
 NSLog(@"json1.a:%@",[data1 objectForKey:@"a"]);
 NSLog(@"json1.b:%@",[data1 objectForKey:@"b"]);
 [json1 release];
 //如果json有嵌套，即value里有array、object，如果再使用objectFromJSONString，程序可能会报错
 //（测试结果表明：使用由网络或得到的php/json_encode生成的json时会报错，但使用NSString定义的json字符串时，解析成功），最好使用objectFromJSONStringWithParseOptions：
 NSString *json2 = @"{\"a\":123, \"b\":\"abc\", \"c\":[456, \"hello\"], \"d\":{\"name\":\"张三\", \"age\":\"32\"}}";
 NSLog(@"json2:%@", json2);
 NSDictionary *data2 = [json2 objectFromJSONStringWithParseOptions:JKParseOptionLooseUnicode];
 NSLog(@"json2.c:%@", [data2 objectForKey:@"c"]);
 NSLog(@"json2.d:%@", [data2 objectForKey:@"d"]);
 [json2 release];
 }