How to serialize a class in IOS sdk (Objective-c)?

Question

How to serialize the following class in objective-c so that it can be used with SBJson?

I get "JSON serialisation not supported for Animal" error when I use this code.

Can someone point out where I am going wrong?

The contents of Animal.h file is as below

#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

The contents of Animal.m file is as below

#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

Make your custom class conform to NSCoding protocol and then serialize it.

For more info, visit the Apple documentation

Also, this link will also help you. As suggested in this link, archive your custom class to NSData and serialize that as provided in the Apple documentation.

Edit Make your Animal.m as follows:

#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

Please check this Property List Programming Guide - Serializing a Property List

and the similar post here: Make a Custom Class Serializable in Objective-c/iPhone?

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

Answer 3

Check the newly introduced NSJSONSerialization class:

NSJSONSerialization class

Answer 4

I think you can check out this if it helps you: Make a Custom Class Serializable

Answer 5

To actually answer your question on how to do it using SBJson: Implement the proxyForJson method. Unless you are serializing an NSArray or NSDictionary you must override this method for serialization to work.

You can see that this is the case by looking at the SBJson source code (in 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;
            }
    ...
    }
}

Implement proxyForJson in Animal.m like this (not tested):

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

Answer 6

See also https://github.com/jsonmodel/jsonmodel

Magical Data Modeling Framework for JSON - allows rapid creation of smart data models. You can use it in your iOS, macOS, watchOS and tvOS apps.

This is also the chosen library for the Objective-c Swagger client.

Answer 7

This open source project JSONCoding makes the whole process pretty simple, using the new sdk class in conjunction with the NSCoding protocol.