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、TouchJSONYAJLJSONKitNextiveJson。详情见这里。既然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:0];

NSLog(@"song info: %@tn",song);

}

　　Foundation对象转换为json数据

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]; }

（编辑：李大同）

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