实现类时出现Objective-C错误

Question

我有这个类

#import <Foundation/Foundation.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

实现文件是这样的：

#import "SubscriptionArray.h"
@implementation SubscriptionArray
@synthesize title,source,htmlUrl;
-(void)dealloc{
    [title release];
    [source release];
    [htmlUrl release];
}
@end

当我像本例中那样使用类时，我会得到一个EXEC_BAD_ACCESS错误：

  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];

        }

有人能帮我吗？P.S.订阅是NSMutableArray

Answer 1

您需要分配SubscriptionArray对象，如下所示：SubscriptionArray *add = [[SubscriptionArray alloc] init];

因此，你的for循环看起来像这样：

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];
}

Answer 2

您需要初始化SubscriptionArray。即

SubscriptionArray *add = [SubscriptionArray new];