NSJSONSerialization介绍

　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

#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 rn");
        return;
    }
    NSArray *songArray = [json objectForKey:song];
    NSLog(song collection: %@rn,songArray);

    _song = songArray;
    self.songIndex = 0;
    NSDictionary *song = [songArray objectAtIndex:song info: %@tn 
NSDictionary *song = [NSDictionary dictionaryWithObjectsAndKeys:i can fly",title4012lengthTomSingerif ([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:%@
  
 
 
 iOS5.0新功能之——NSJSONSerialization解析JSON数据
 

 
 
 
 
 
 
 
 
 
 
  
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];  }
  
                        
（编辑：李大同）
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