How to use NSCoder

Question

I am developing iphone application.

I use NSCoder.

MyApplication.h

#define ITEMS_KEY @"items"
#define CATEGORIES_KEY @"categories"


#import <UIKit/UIKit.h>


@interface MyApplicationData : NSObject <NSCoding, NSCopying> {
    NSMutableArray* items;
    NSMutableArray* categories;
}

@property (nonatomic ,retain) NSMutableArray* items;
@property (nonatomic, retain) NSMutableArray* categories;


@end

Myapplication.m

#import "MyApplicationData.h"


@implementation MyApplicationData

@synthesize items;
@synthesize categories;

#pragma mark NSCoding
- (void)encodeWithCoder:(NSCoder *)aCoder{
  [aCoder encodeObject:items forKey:ITEMS_KEY];
  [aCoder encodeObject:categories forKey:CATEGORIES_KEY];
}

-(id)initWithCoder:(NSCoder *)aDecoder{
  if(self = [super init]){
    self.items = [aDecoder decodeObjectForKey:ITEMS_KEY];
    self.categories = [aDecoder decodeObjectForKey:CATEGORIES_KEY];
  }
  return self;
}

#pragma mark -
#pragma mark NSCopying
-(id)copyWithZone:(NSZone *)zone{
  MyApplicationData* copy = [[[self class]allocWithZone:zone]init];
  items = [self.items copy];
  categories = [self.categories copy];
  return copy;
}

@end

But warnning.

'NSCoder' may not respond to '-decodeDataObjectForKey'

How to use NSCoder?

Answer 1

Use -decodeObjectForKey: and read the documentation.