iOS:单例返回空

Question

我有一个单例，我将数据传递给它，但它返回 null，你能帮我解决我的情况吗？提前致谢:)

这是我的代码

Card.h

@property (weak,nonatomic) NSString *email;
@property (weak,nonatomic) NSString *fName;
@property (weak,nonatomic) NSString *lName;
@property (weak,nonatomic) NSString *category;

+(Card *)getCard;

卡片.m

@synthesize email;
@synthesize fName;
@synthesize lName;
@synthesize category;

static csCard *instance;

+(Card *) getCard
{
    @synchronized (self)
    {
        if(instance == nil)
        {
            instance = [[Card alloc]init];
        }
    }
    return instance;
}

- (id) init{

    self.email = [[NSUserDefaults standardUserDefaults]stringForKey:@"email"];
    self.fName = [[NSUserDefaults standardUserDefaults]stringForKey:@"firstName"];
    self.lName = [[NSUserDefaults standardUserDefaults]stringForKey:@"lastName"];
    self.category = @"TestCategory";

    return self;
}

这是我的测试代码，看看它是否正常工作

测试.m

Card *card = [Card getCard];
    [card setEmail:self.emailField.text];
    NSLog(@"%@",card.email);

但是这段代码给我(null)

Answer 1

像这样修改你的类。

Card.h

@property (strong,nonatomic) NSString *email; //Let the modal be strong property
@property (strong,nonatomic) NSString *fName;
@property (strong,nonatomic) NSString *lName;
@property (strong,nonatomic) NSString *category;

+(Card *)getCard;

卡片.m

static Card *instance;

+(Card *) getCard
{
    @synchronized (self)
    {
        if(instance == nil)
        {
            instance = [[Card alloc]init];
        }
    }
    return instance;
}
- (NSString)email{
return [[NSUserDefaults standardUserDefaults]stringForKey:@"email"];
}

- (void)setEmail:(NSString)email{
[[NSUserDefaults standardUserDefaults] setString:email forkey:@"email"];
}

不需要覆盖初始化

在你的测试课上

Card *card = [Card getCard];
    [card setEmail:self.emailField.text];
    NSLog(@"%@",card.email);