1 前言
通过 NSJSONSerialization 这个类的 dataWithJSONObject:options:error:方法来实现,Array 和 dictionary 序列化成 JSON 对象。方便在网络中传输。

2 代码实例
TestDemo.m

[plain]
(void)converseToJson{ 
    NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] init]; 
    [dictionary setValue:@"Archy" forKey:@"First Name"]; 
    [dictionary setValue:@"Robbins" forKey:@"Last Name"]; 
    [dictionary setValue:[NSNumber numberWithUnsignedInteger:51] forKey:@"Age"]; 
    NSArray *arrayOfArchysChildren = [[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:arrayOfArchysChildren forKey:@"children"]; 
    NSError *error = nil; 
    //NSJSONWritingPrettyPrinted:指定生成的JSON数据应使用空格旨在使输出更加可读。如果这个选项是没有设置,最紧凑的可能生成JSON表示。 
    NSData *jsonData = [NSJSONSerialization 
                        dataWithJSONObject:dictionary options:NSJSONWritingPrettyPrinted error:&error]; 
    if ([jsonData length] > 0 && error == nil){ 
        NSLog(@"Successfully serialized the dictionary into data."); 
        //NSData转换为String 
        NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding]; 
        NSLog(@"JSON String = %@", jsonString); 
    } 
    else if ([jsonData length] == 0 && 
             error == nil){ 
        NSLog(@"No data was returned after serialization."); 
    } 
    else if (error != nil){ 
        NSLog(@"An error happened = %@", error); 
    } 
     
}

-(void)converseToJson{
    NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] init];
    [dictionary setValue:@"Archy" forKey:@"First Name"];
    [dictionary setValue:@"Robbins" forKey:@"Last Name"];
    [dictionary setValue:[NSNumber numberWithUnsignedInteger:51] forKey:@"Age"];
    NSArray *arrayOfArchysChildren = [[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:arrayOfArchysChildren forKey:@"children"];
    NSError *error = nil;
    //NSJSONWritingPrettyPrinted:指定生成的JSON数据应使用空格旨在使输出更加可读。如果这个选项是没有设置,最紧凑的可能生成JSON表示。
    NSData *jsonData = [NSJSONSerialization
                        dataWithJSONObject:dictionary options:NSJSONWritingPrettyPrinted error:&error];
    if ([jsonData length] > 0 && error == nil){
        NSLog(@"Successfully serialized the dictionary into data.");
        //NSData转换为String
        NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
        NSLog(@"JSON String = %@", jsonString);
    }
    else if ([jsonData length] == 0 &&
             error == nil){
        NSLog(@"No data was returned after serialization.");
    }
    else if (error != nil){
        NSLog(@"An error happened = %@", error);
    }
   
}
控制台结果

2013-05-13 17:14:26.087 ToJsonTest[4890:303] Successfully serialized the dictionary into data.

2013-05-13 17:14:26.089 ToJsonTest[4890:303] JSON String = {

"children" : [

"Anthony's Son 1",

"Anthony's Daughter 1",

"Anthony's Son 2",

"Anthony's Son 3",

"Anthony's Daughter 2"

],

"Age" : 51,

"First Name" : "Archy",

"Last Name" : "Robbins"

}