JSONKit

1.将字典或者数组反序列化为NSString.
    NSMutableDictionary *jsonDic = [NSMutableDictionary dictionary];
    NSMutableDictionary *alert = [NSMutableDictionary dictionary];
    NSMutableDictionary *aps = [NSMutableDictionary dictionary];
    [alert setObject:@"a msg come!" forKey:@"body"];
    [aps setObject:alert forKey:@"alert"];
    [aps setObject:@"3" forKey:@"bage" ];
    [aps setObject:@"def.mp3" forKey:@"sound"];
    [jsonDic setObject:aps forKey:@"aps"];
   
    NSString *strJson = [jsonDic JSONString];
   
    NSLog(@"%@",strJson);


2.将NSString反序列化为数组、字典.
    NSDictionary *result = [strJson  objectFromJSONString];
或者
   NSDictionary *result = [dataJson  objectFromJSONData];
   

    NSLog(@"333%@",result);

JSON和Object-C中数据类型的映射关系如下表所示

JSON	Objective-C
null	NSNull
true and false	NSNumber
Number	NSNumber
String	NSString
Array	NSArray
Object	NSDictionary

下面写一个简单的程序使用一下JSONKit（只需下载头文件以及源文件，放在项目目录下）

#import <Foundation/Foundation.h>
#import "lib/JSONKit.h"

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    NSString *res = nil;

    /*
     * json格式编码
     */

    //字符串
    NSString *str = @"this is a nsstring";
    res = [str JSONString];
    NSLog(@"res= %@", [NSString stringWithString: res]);
    //res= "this is a nsstring"


    //数组
    NSArray *arr = [[NSArray alloc] initWithObjects:@"One",@"Two",@"Three",nil];
    res = [arr JSONString];
    NSLog(@"res= %@", [NSString stringWithString: res]);
    [arr release];
    //res= ["One","Two","Three"]


    //字典类型（对象）
    NSArray *arr1 = [NSArray arrayWithObjects:@"dog",@"cat",nil];
    NSArray *arr2 = [NSArray arrayWithObjects:[NSNumber numberWithBool:YES],[NSNumber numberWithInt:30],nil];
    NSDictionary *dic = [NSDictionary dictionaryWithObjectsAndKeys:arr1,@"pets",arr2,@"other",nil];
    res = [dic JSONString];
    NSLog(@"res= %@", [NSString stringWithString: res]);
    //res= {"pets":["dog","cat"],"other":[true,30]}


    /*
     * json格式解码
     */
    JSONDecoder *jd=[[JSONDecoder alloc] init];

    //针对NSData数据
    NSData *data = [dic JSONData];
    NSDictionary *ret = [jd objectWithData: data];
    NSLog(@"res= %@", [ret objectForKey:@"pets"]);
    //res= (
    //  dog,
    //  cat
    //)
    NSLog(@"res= %@", [[ret objectForKey:@"other"] objectAtIndex:0]);
    //res= 1

    //针对NSString字符串数据
    NSString *nstr = [dic JSONString];
    NSDictionary *ret2 = [jd objectWithUTF8String:(const unsigned char *)[nstr UTF8String] length:(unsigned int)[nstr length]];
    NSLog(@"res= %d", [[ret2 objectForKey:@"pets"] indexOfObject:@"cat"]);
    //res= 1
    NSLog(@"res= %@", [[ret2 objectForKey:@"other"] objectAtIndex:1]);
    //res= 30

    [jd release];

    [pool drain];
    return 0;
}