如何在IOS sdk（Objective-c）中序列化一個類？

Question

如何序列化Objective-C中的以下類，以便它可以與SBJson一起使用？

當我使用此代碼時，出現「Animal不支持JSON序列化」錯誤。

有人可以指出我要去哪裏嗎？

Animal.h文件的內容是如下

#import <UIKit/UIKit.h> 

@interface Animal : NSObject<NSCoding> { 
    NSString *name; 
    NSString *description; 
    NSString *imageURL; 
} 

@property (nonatomic, retain) NSString *name; 
@property (nonatomic, retain) NSString *description; 
@property (nonatomic, retain) NSString *imageURL; 

-(id)initWithName:(NSString *)n description:(NSString *)d url:(NSString *)u; 

@end 

Animal.m文件的內容是如下

#import "Animal.h" 

@implementation Animal 
@synthesize name, description, imageURL; 

-(id)initWithName:(NSString *)n description:(NSString *)d url:(NSString *)u { 
    self.name = n; 
    self.description = d; 
    self.imageURL = u; 
    return self; 
} 

- (id)initWithCoder:(NSCoder *)aDecoder 
{ 
    if(self = [super initWithCoder:aDecoder]) 
    { 
     name = [[aDecoder decodeObjectForKey:@"name"] retain]; 
     description = [[aDecoder decodeObjectForKey:@"description"] retain]; 
     imageURL = [[aDecoder decodeObjectForKey:@"imageURL"] retain]; 
    } 
    return [self initWithName:name description:description url:imageURL]; 
} 

- (void)encodeWithCoder:(NSCoder *)encoder 
{ 
    [super encodeWithCoder:encoder]; 
    [encoder encodeObject:name forKey:@"name"]; 
    [encoder encodeObject:description forKey:@"description"]; 
    [encoder encodeObject:imageURL forKey:@"imageURL"]; 
}  

@end 

Answer 1

讓您的自定義類符合NSCoding協議，然後序列化。

欲瞭解更多信息，請訪問Apple documentation

此外，這也link會幫助你。 正如此鏈接中所建議的，將您的自定義類歸檔到NSData並按照Apple文檔中的說明序列化。

編輯 讓你Animal.m如下：

#import "Animal.h" 

@implementation Animal 
@synthesize name, description, imageURL; 

-(id)initWithName:(NSString *)n description:(NSString *)d url:(NSString *)u { 
    self = [super init]; 
    if(self) 
    { 
     self.name = n; 
     self.description = d; 
     self.imageURL = u; 
    } 
    return self; 
} 

- (id)initWithCoder:(NSCoder *)aDecoder 
{ 
    self = [super init]; 
    if(self) 
    { 
     self.name = [aDecoder decodeObjectForKey:@"name"]; 
     self.description = [aDecoder decodeObjectForKey:@"description"]; 
     self.imageURL = [aDecoder decodeObjectForKey:@"imageURL"]; 
    } 
    return self; 
} 

- (void)encodeWithCoder:(NSCoder *)encoder 
{ 
    [encoder encodeObject:name forKey:@"name"]; 
    [encoder encodeObject:description forKey:@"description"]; 
    [encoder encodeObject:imageURL forKey:@"imageURL"]; 
}  

@end 

Answer 2

請檢查該Property List Programming Guide - Serializing a Property List

和類似的帖子在這裏： Make a Custom Class Serializable in Objective-c/iPhone?

Object serialization in XML format using Obj-C/iPhone SDK

Answer 3

檢查新引進NSJSONSerialization類：

NSJSONSerialization class

Answer 4

我想你可以看看這個，如果它可以幫助你：Make a Custom Class Serializable

Answer 5

要真正回答你關於如何使用SBJson做問題：實施方法proxyForJson。除非要序列化NSArray或NSDictionary，否則必須重寫此方法以使序列化正常工作。

你可以看到，這樣的話通過查看SBJson源代碼（在SBJsonWriter.m）：

- (NSData*)dataWithObject:(id)object {  
... 
    if ([object isKindOfClass:[NSDictionary class]]) 
       ok = [streamWriter writeObject:object]; 

      else if ([object isKindOfClass:[NSArray class]]) 
       ok = [streamWriter writeArray:object]; 

      else if ([object respondsToSelector:@selector(proxyForJson)]) 
       return [self dataWithObject:[object proxyForJson]]; 
      else { 
       self.error = @"Not valid type for JSON"; 
       return nil; 
      } 
    ... 
    } 
} 

在Animal.m這樣的（未測試）實施proxyForJson：

- (NSDictionary*) proxyForJson 
{ 
return [NSDictionary dictionaryWithObjectsAndKeys:self.name, @"name", 
                self.description, @"description", 
                self.imageURL, @"imageURL", 
                nil]; 
} 

Answer 6

這個開源項目JSONCoding使整個過程非常簡單，使用新的sdk類和NSCoding協議。