将iOS目标c对象转换为JSON字符串

Question

我有一个客观的C类,

@interface message : NSObject {
 NSString *from;
 NSString *date;
 NSString *msg;
}

我有一个NSMutableArray这个消息类的实例.我想使用iOS 5 SDK中的新JSONSerialization API将NSMutableArray中的所有实例序列化为JSON文件.我怎样才能做到这一点 ？

是通过迭代NSArray中每个元素的实例来创建每个键的NSDictionary吗？有人可以帮助解决这个问题的代码吗？我无法在Google中取得好成绩,因为"JSON"会将结果偏向服务器端调用和数据传输而不是序列化.非常感谢.

编辑:

NSError *writeError = nil; 
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:notifications options:NSJSONWritingPrettyPrinted error:&writeError];
NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding]; 
NSLog(@"JSON Output: %@", jsonString);

Answer 1

编辑:我已经制作了一个虚拟应用程序,应该是一个很好的例子.

我从你的代码片段创建一个Message类;

//Message.h
@interface Message : NSObject {
    NSString *from_;
    NSString *date_;
    NSString *msg_;
}

@property (nonatomic, retain) NSString *from;
@property (nonatomic, retain) NSString *date;
@property (nonatomic, retain) NSString *msg;

-(NSDictionary *)dictionary;

@end

//Message.m
#import "Message.h"

@implementation Message

@synthesize from = from_;
@synthesize date = date_;
@synthesize msg = mesg_;

-(void) dealloc {
    self.from = nil;
    self.date = nil;
    self.msg = nil;
    [super dealloc];
}

-(NSDictionary *)dictionary {
    return [NSDictionary dictionaryWithObjectsAndKeys:self.from,@"from",self.date,    @"date",self.msg, @"msg", nil];
}

然后我在AppDelegate中设置了两个消息的NSArray.诀窍在于顶级对象(在您的情况下是通知)不仅需要可序列化,而且通知包含的所有元素也是如此:这就是我在Message类中创建字典方法的原因.

//AppDelegate.m
...
Message* message1 = [[Message alloc] init];
Message* message2 = [[Message alloc] init];

message1.from = @"a";
message1.date = @"b";
message1.msg = @"c";

message2.from = @"d";
message2.date = @"e";
message2.msg = @"f";

NSArray* notifications = [NSArray arrayWithObjects:message1.dictionary, message2.dictionary, nil];
[message1 release];
[message2 release];


NSError *writeError = nil; 
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:notifications options:NSJSONWritingPrettyPrinted error:&writeError];
NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding]; 
NSLog(@"JSON Output: %@", jsonString);

@end

因此,运行应用程序时的输出是:

2012-05-11 11:58:36.018 stack [3146:f803] JSON输出:[{"msg":"c","from":"a","date":"b"},{"msg" :"f","from":"d","date":"e"}]

原始答案:

是这个你正在寻找的文件？

Answer 2

现在,您可以使用JSONModel轻松解决此问题.JSONModel是一个基于Class一般序列化/反序列化对象的库.你甚至可以使用基于财产像非NSObject的int,short和float.它还可以满足嵌套复杂的JSON.它为您处理错误检查.

反序列化示例.在头文件中:

#import "JSONModel.h"

@interface Message : JSONModel 
@property (nonatomic, strong) NSString* from;
@property (nonatomic, strong) NSString* date;
@property (nonatomic, strong) NSString* message;
@end

在实施文件中:

#import "JSONModelLib.h"
#import "yourPersonClass.h"

NSString *responseJSON = /*from somewhere*/;
Message *message = [[Message alloc] initWithString:responseJSON error:&err];
if (!err)
{
   NSLog(@"%@  %@  %@", message.from, message.date, message.message):
}

序列化示例.在实现文件中:

#import "JSONModelLib.h"
#import "yourPersonClass.h"

Message *message = [[Message alloc] init];
message.from = @"JSON beast";
message.date = @"2012";
message.message = @"This is the best method available so far";

NSLog(@"%@", [person toJSONString]);