Objective-C error while implementing class?

I have this class

#import <Foundation/F开发者_运维问答oundation.h>

@interface SubscriptionArray : NSObject{
    NSString *title;
    NSString *source;
    NSString *htmlUrl;
}

@property (nonatomic,retain) NSString *title;
@property (nonatomic,retain) NSString *source;
@property (nonatomic,retain) NSString *htmlUrl;

@end

and the implementation file is this one:

#import "SubscriptionArray.h"

@implementation SubscriptionArray
@synthesize title,source,htmlUrl;

-(void)dealloc{
    [title release];
    [source release];
    [htmlUrl release];
}

@end

When I use the class like in this example I get an EXEC_BAD_ACCESS error:

  for (NSDictionary *element in subs){
            SubscriptionArray *add;
            add.title=[element objectForKey:@"title"];   //ERROR Happens at this line
            add.source=[element objectForKey:@"htmlUrl"];
            add.htmlUrl=[element objectForKey:@"id"];
            [subscriptions addObject:add];


        }

Can someone help me? P.S. Subscriptions is a NSMutableArray

You need to allocate your SubscriptionArray object like so: SubscriptionArray *add = [[SubscriptionArray alloc] init];

Your for loop will therefore look something like this:

for (NSDictionary *element in subs){
        SubscriptionArray *add = [[SubscriptionArray alloc] init];
        add.title=[element objectForKey:@"title"];
        add.source=[element objectForKey:@"htmlUrl"];
        add.htmlUrl=[element objectForKey:@"id"];
        [subscriptions addObject:add];
        [add release];
}

You need to initialize your SubscriptionArray. i.e.

SubscriptionArray *add = [SubscriptionArray new];