1.ios解析json
使用开源json包，项目地址：
     http://stig.github.com/json-framework/
NSData * responseData = http://www.mamicode.com/[respones responseData];
      
     NSString * strResponser = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
SBJsonParser * parser = [[SBJsonParser alloc]init];
     NSMutableDictionary *dicMessageInfo = [parser objectWithString:strResponser]; // 解析成json解析对象
[parser release];
     //发送者
     NSString * sender = [dicMessageInfo objectForKey:@"sender"];

2.json嵌套对象解析：
//要上传的字符串
    NSString *dataStr=[[NSString alloc] initWithString:@"{\"cross\":{\"1\":\"true\",\"2\":\"false\",\"3\":\"true\"}}"];
//获取响应返回字符串
NSData * responseData = http://www.mamicode.com/[respones responseData];
        
        NSString * strResponser = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
//嵌套解析
SBJsonParser * parser = [[SBJsonParser alloc]init];
            
            NSMutableDictionary *dicMessageInfo = [parser objectWithString:strResponser]; // 解析成json解析对象
            
            NSMutableDictionary * cross = [dicMessageInfo objectForKey:@"cross"];
            
            NSString *cross1= [cross objectForKey:@"1"];
            //解析json到各个字符串
            //发送者
            [parser release];
            NSLog(@"cross1: %@",cross1);
3.拼接json字符串

通过使用SBJson中的SBJsonWriter类的方法- (NSString*)stringWithObject:(id)value可以将一个对象中的值格式化为json字符串，符合key/value格式的数据封装到NSDictionary后可以使用该方法进行格式化，其他数据通过拼接字符串的方式格式化。
在拼接过程中可以使用类NSMutableString的方法：
- (void)appendString:(NSString *)aString;、
- (void)appendFormat:(NSString *)format, ... NS_FORMAT_FUNCTION(1,2);
动态添加字符串。
拼接的字符串可通过json在线验证的方式验证其格式是否正确，网址为：
http://jsonlint.com/
-(NSString *) getJsonString
{
    NSMutableString *json = [NSMutableString stringWithCapacity:128];
    NSString *jsonString=nil;
    SBJsonWriter *writer = [[SBJsonWriter alloc] init];
    [json appendString:@"{\"data\":{"];
    [json appendFormat:@"\"%@\":\"%d\",",@"reset",reset];
    if(missionStatus!=NULL)
    {
        jsonString=[writer stringWithObject:status];
        if(jsonString!=NULL)
        {
            [json appendString:@"\"status\":"];
            [json appendString:jsonString];
        }
    }
    [json appendString:@"}}"];
    return json;
}
4.利用多个NSDictionary，拼接多层嵌套的json字符串，减少因手工拼接忘记加引号导致的json格式错误
示例代码：
NSDictionary *dataDictionary= [NSDictionary dictionaryWithObjectsAndKeys:mac,@"mac",
                                   game,@"game",
                                   devicetoken,@"devicetoken",
                                   device,@"device",
                                   gv,@"gv",
                                   lang,@"lang",
                                   os,@"os",
                                   hardware,@"hardware",
                                   down,@"down",nil];
    NSDictionary *parmDictionary= [NSDictionary dictionaryWithObjectsAndKeys:@"getSession",@"act",
                                   dataDictionary,@"data",nil];
    NSDictionary *jsonDictionary=[NSDictionary dictionaryWithObjectsAndKeys:pv,@"pv",
                                  parmDictionary,@"param",nil];
    SBJsonWriter *writer = [[SBJsonWriter alloc] init];
    
    NSString *jsonString=nil;
    jsonString=[writer stringWithObject:jsonDictionary];
    NSLog(@"%@",jsonString);
5.json字符串在线校验网址：
http://jsonlint.com/

ios 中使用SBJson拼接和解析json