NSUserdefaults 不适用于 NSKeyedArchiver

Question

我有一个 NSMutableArray，里面装满了我想保存的 Movie 类的对象，但它不起作用，我不知道为什么...

电影.h：

@interface Movie : NSObject <NSCoding>{
    NSString *name;
    int year;
    int length;
    NSString *file_size;
    int rating;
    NSArray *genre;
    NSString *plot;
}

@property (nonatomic, retain) NSString *name;
@property (nonatomic, assign) int year;
@property (nonatomic, assign) int length;
@property (nonatomic, retain, retain) NSString *file_size;
@property (nonatomic, assign) int rating;
@property (nonatomic, retain) NSArray *genre;
@property (nonatomic, retain) NSString *plot;

-(id) initWithName:(NSString*)newName year:(int)newYear length:(int)newLength filesize:(NSString*)newFileSize rating:(int)newRating genre:(NSArray*)newGenre plot:(NSString*)newPlot;
- (void) encodeWithCoder : (NSCoder *)encode ;
- (id) initWithCoder : (NSCoder *)decode;

@end

电影.m：

@implementation Movie

@synthesize name;
@synthesize year;
@synthesize length;
@synthesize file_size;
@synthesize rating;
@synthesize genre;
@synthesize plot;

-(id)initWithName:(NSString *)newName year:(int)newYear length:(int)newLength filesize:(NSString *)newFileSize rating:(int)newRating genre:(NSArray *)newGenre plot:(NSString *)newPlot{
    self.name = newName;
    self.year = newYear;
    self.length = newLength;
    self.file_size = newFileSize;
    self.rating = newRating;
    self.genre = newGenre;
    self.plot = newPlot;
    return self;
}
- (void)encodeWithCoder:(NSCoder *)encode;
{
    [encode encodeObject:name forKey:@"name"];
    [encode encodeInt32:year forKey:@"year"];
    [encode encodeInt32:length forKey:@"length"];
    [encode encodeObject:file_size forKey:@"file_size"];
    [encode encodeInt32:rating forKey:@"rating"];
    [encode encodeObject:genre forKey:@"genre"];
    [encode encodeObject:plot forKey:@"plot"];
}

- (id)initWithCoder:(NSCoder *)decode;
{
        NSString *name_decode = [decode decodeObjectForKey:@"name"];
        int year_decode = [decode decodeInt32ForKey:@"year"];
        int length_decode = [decode decodeInt32ForKey:@"length"];
    NSString *file_size_decode = [decode decodeObjectForKey:@"file_size"];
    int rating_decode = [decode decodeInt32ForKey:@"rating"];
    NSArray *genre_decode = [decode decodeObjectForKey:@"genre"];
    NSString *plot_decode =[decode decodeObjectForKey:@"plot"];
    return [self initWithName:name_decode year:year_decode length:length_decode filesize:file_size_decode rating:rating_decode genre:genre_decode plot:plot_decode];
}

@end

保存操作（电影是包含我的对象的 NSMutableArray）：

NSUserDefaults *userDefault=[NSUserDefaults standardUserDefaults];
    NSData *encodedData = [NSKeyedArchiver archivedDataWithRootObject:Movies];
    [userDefault setObject:encodedData forKey:[NSString stringWithFormat:@"MOVIES"]];

加载动作：

NSData *decodedData = [userDefault objectForKey: [NSString stringWithFormat:@"MOVIES"]];
    NSArray *decodedArray =[NSKeyedUnarchiver unarchiveObjectWithData: decodedData];

返回的数组总是（空）...我不知道 我尝试了几种在 Internet 和/或 stackoverflow 上找到的不同类型的代码 sn-ps

Answer 1

您的Movie initWithName... 方法不正确。它必须是：

- (instancetype)initWithName:(NSString *)newName year:(int)newYear length:(int)newLength filesize:(NSString *)newFileSize rating:(int)newRating genre:(NSArray *)newGenre plot:(NSString *)newPlot {
    self = [super init];
    if (self) {
        self.name = newName;
        self.year = newYear;
        self.length = newLength;
        self.file_size = newFileSize;
        self.rating = newRating;
        self.genre = newGenre;
        self.plot = newPlot;
    }

    return self;
}

另外，您似乎在学习一个非常过时的教程。

1. 您无需为您的属性声明 ivars。
2. 您不需要拨打@synthesize。
3. 您应该使用 ARC 而不是 MRC，因此您的 retain 属性应该是 strong（认为 NSString 属性应该是 copy。
4. 您的init 方法应返回instancetype，而不是id。

考虑到所有这些，您的 Movie 类应如下所示：

电影.h

@interface Movie : NSObject <NSCoding>

@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) int year;
@property (nonatomic, assign) int length;
@property (nonatomic, copy) NSString *file_size;
@property (nonatomic, assign) int rating;
@property (nonatomic, strong) NSArray *genre;
@property (nonatomic, copy) NSString *plot;

- (instancetype)initWithName:(NSString *)newName year:(int)newYear length:(int)newLength filesize:(NSString *)newFileSize rating:(int)newRating genre:(NSArray *)newGenre plot:(NSString *)newPlot;

@end

电影.m

@implementation Movie

- (instancetype)initWithName:(NSString *)newName year:(int)newYear length:(int)newLength filesize:(NSString *)newFileSize rating:(int)newRating genre:(NSArray *)newGenre plot:(NSString *)newPlot {
    self = [super init];
    if (self) {
        _name = newName;
        _year = newYear;
        _length = newLength;
        _file_size = newFileSize;
        _rating = newRating;
        _genre = newGenre;
        _plot = newPlot;
    }

    return self;
}

- (void)encodeWithCoder:(NSCoder *)encode;
{
    [encode encodeObject:self.name forKey:@"name"];
    [encode encodeInt32:self.year forKey:@"year"];
    [encode encodeInt32:self.length forKey:@"length"];
    [encode encodeObject:self.file_size forKey:@"file_size"];
    [encode encodeInt32:self.rating forKey:@"rating"];
    [encode encodeObject:self.genre forKey:@"genre"];
    [encode encodeObject:self.plot forKey:@"plot"];
}

- (instancetype)initWithCoder:(NSCoder *)decode;
{
    NSString *name_decode = [decode decodeObjectForKey:@"name"];
    int year_decode = [decode decodeInt32ForKey:@"year"];
    int length_decode = [decode decodeInt32ForKey:@"length"];
    NSString *file_size_decode = [decode decodeObjectForKey:@"file_size"];
    int rating_decode = [decode decodeInt32ForKey:@"rating"];
    NSArray *genre_decode = [decode decodeObjectForKey:@"genre"];
    NSString *plot_decode =[decode decodeObjectForKey:@"plot"];
    return [self initWithName:name_decode year:year_decode length:length_decode filesize:file_size_decode rating:rating_decode genre:genre_decode plot:plot_decode];
}

@end

您没有展示如何创建和填充您的 Movies 变量（应命名为 movies，而不是 Movies。确保它不是 nil。

另外，不要不必要地使用stringWithFormat。

您的保存代码应该是：

NSUserDefaults *userDefault=[NSUserDefaults standardUserDefaults];
NSData *encodedData = [NSKeyedArchiver archivedDataWithRootObject:movies];
[userDefault setObject:encodedData forKey:@"MOVIES"];

你的加载代码应该是：

NSData *decodedData = [userDefault objectForKey:@"MOVIES"];
NSArray *decodedArray = [NSKeyedUnarchiver unarchiveObjectWithData: decodedData];

Answer 2

一个快速测试是查看可变数组本身是否实际上不是 nil。在将可变数组设置为 userDefaults 之前尝试输出可变数组。

确保可变数组在尝试向其添加对象之前已初始化。

movies = [[NSMutableArray alloc] init];