ios5中apple增加了解析JSON的api——NSJSONSerialization。网上已经有人做过测试，NSJSONSerialization在效率上完胜SBJSON、TouchJSON、YAJL、JSONKit、NextiveJson。详情见这里。既然apple为我们提供了这么良好的工具，我们没理由不用吧。

　　NSJSONSerialization提供了将JSON数据转换为Foundation对象（一般都是NSDictionary和NSArray）和Foundation对象转换为JSON数据（可以通过调用isValidJSONObject来判断Foundation对象是否可以转换为JSON数据）。

　　下面提供一个从豆瓣电台下载的json数据转换的代码

　　

View Code

#define kGlobalQueue    dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0)

#define kDoubanUrl      @"http://douban.fm/j/mine/playlist?type=n&h=&channel=0&from=mainsite&r=4941e23d79"

-(void) loadJsonData:(NSURL *)url

{

    dispatch_async(kGlobalQueue, ^{

        NSData *data = [NSData dataWithContentsOfURL:url];

        [self performSelectorOnMainThread:@selector(parseJsonData:) withObject:data waitUntilDone:NO];

    });

}

-(void) parseJsonData:(NSData *)data

{

    NSError *error;

    NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];

    if (json == nil) {

        NSLog(@"json parse failed \r\n");

        return;

    }

    NSArray *songArray = [json objectForKey:@"song"];

    NSLog(@"song collection: %@\r\n",songArray);

 

    _song = songArray;

    self.songIndex = 0;

    NSDictionary *song = [songArray objectAtIndex:0];

    NSLog(@"song info: %@\t\n",song);

}

　　Foundation对象转换为json数据

View Code

NSDictionary *song = [NSDictionary dictionaryWithObjectsAndKeys:@"i can fly",@"title",@"4012",@"length",@"Tom",@"Singer", nil];

    if ([NSJSONSerialization isValidJSONObject:song])

    {

        NSError *error;

        NSData *jsonData = [NSJSONSerialization dataWithJSONObject:song options:NSJSONWritingPrettyPrinted error:&error];

        NSString *json =[[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];

        NSLog(@"json data:%@",json);

    }

 

 

 

 

iOS5.0新功能之——NSJSONSerialization解析JSON数据

 

- (IBAction)touchWriteButton:(id)sender {
      NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] init];
      [dictionary setValue:@"Anthony" forKey:@"First Name"];
      [dictionary setValue:@"Robbins" forKey:@"Last Name"];
      [dictionary setValue:[NSNumber numberWithUnsignedInteger:51] forKey:@"Age"];
      NSArray *arrayOfAnthonysChildren = [[NSArray alloc] initWithObjects:@"Anthony's Son 1", @"Anthony's Daughter 1", @"Anthony's Son 2", @"Anthony's Son 3", @"Anthony's Daughter 2", nil];
      [dictionary setValue:arrayOfAnthonysChildren forKey:@"children"];
      NSError *error = nil;
      NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dictionary options:NSJSONWritingPrettyPrinted error:&error];
      if (error) {
         NSLog(@"dic->%@",error);
      }
      [dictionary release];
      BOOL succeed = [jsonData writeToFile:JSON_PATH atomically:YES];
      if (succeed) {
          NSLog(@"Save succeed");
      }else {
          NSLog(@"Save fail");
      }
 }

 

 

- (IBAction)touchReadButton:(id)sender {
       NSData *jsonData = [[NSData alloc] initWithContentsOfFile:JSON_PATH];     /* Now try to deserialize the JSON object into a dictionary */
       NSError *error = nil;
       id jsonObject = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingAllowFragments error:&error];
      if (jsonObject != nil && error == nil){
          NSLog(@"Successfully deserialized...");
          if ([jsonObject isKindOfClass:[NSDictionary class]]){
               NSDictionary *deserializedDictionary = (NSDictionary *)jsonObject;
               NSLog(@"Dersialized JSON Dictionary = %@", deserializedDictionary);
          } else if ([jsonObject isKindOfClass:[NSArray class]]){
              NSArray *deserializedArray = (NSArray *)jsonObject;
              NSLog(@"Dersialized JSON Array = %@", deserializedArray);
          } else {
              NSLog(@"An error happened while deserializing the JSON data.");
          }
      }
      [jsonData release];
  }