ios - 在“init”中初始化的对象无法在“viewDidLoad”中访问

Question

我有一个奇怪的问题:我以“init”方法加载对象数据。当我尝试在“viewDidLoad”中访问它时，我的应用程序崩溃。这是代码:

@interface UploadCenterViewController () {
    NSMutableArray *videos;
}

@end

@implementation UploadCenterViewController 

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];  
    if (self) {
        if (![self loadVideos]) {
            [self saveVideos];
        }
    }

    return self;
}

-(void)saveVideos {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    NSData *encodedData = [NSKeyedArchiver archivedDataWithRootObject:videos];
    [defaults setObject:encodedData forKey:@"VIDEOS"];
    [defaults synchronize];
}

-(bool)loadVideos {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    NSData *encodedData = [defaults objectForKey:@"VIDEOS"];
    if (encodedData) {
        videos = (NSMutableArray *)[NSKeyedUnarchiver unarchiveObjectWithData:encodedData];

        NSLog(@"array size: %d", [videos count]);

        return true;
    } else {
        videos = [[NSMutableArray alloc] init];
        return false;
    }
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSLog(@"%d", [videos count]);
}

加载数据时，“视频”数组包含一个对象。在“viewDidLoad”中访问它时，整个应用程序崩溃。

有人有主意吗？

Answer 1

将videos声明为@property，并在各处将其用作self.videos。崩溃是由于分配了值videos即将被释放。 videos的范围仅在该方法内，因此可能会崩溃。由于要在该方法之外使用此方法，因此需要保留它，并且可以使用@property进行操作，如下所述。

例如:

@interface UploadCenterViewController () {}

@property(nonatomic, strong) NSMutableArray *videos;

@end

-(void)saveVideos {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    NSData *encodedData = [NSKeyedArchiver archivedDataWithRootObject:self.videos];
    [defaults setObject:encodedData forKey:@"VIDEOS"];
    [defaults synchronize];
}

-(bool)loadVideos {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    NSData *encodedData = [defaults objectForKey:@"VIDEOS"];
    if (encodedData) {
        self.videos = (NSMutableArray *)[NSKeyedUnarchiver unarchiveObjectWithData:encodedData];
        NSLog(@"array size: %d", [self.videos count]);
        return true;
    } else {
        self.videos = [[NSMutableArray alloc] init];
        return false;
    }
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSLog(@"%d", [self.videos count]);
}