Question

我有一个名为Occasion的自定义对象，定义如下：

#import <Foundation/Foundation.h>


@interface Occasion : NSObject {

NSString *_title;
NSDate *_date;
NSString *_imagePath;    

}

@property (nonatomic, retain) NSString *title;
@property (nonatomic, retain) NSDate *date;
@property (nonatomic, retain) NSString *imagePath;

现在我有一个NSMutableArray of Occasions，我想保存到NSUserDefaults。我知道这是不可能的，所以我想知道哪种方法最简单？如果序列化是答案，那么如何？因为我阅读了文档但却无法理解它的完整工作方式。

Answer 1

您应该使用类似NSKeyedArchiver的内容将数组序列化为NSData，将其保存到NSUserDefaults，然后再使用NSKeyedUnarchiver对其进行反序列化：

NSData *serialized = [NSKeyedArchiver archivedDataWithRootObject:myArray];
[[NSUserDefaults standardUserDefaults] setObject:serialized forKey:@"myKey"];

//...

NSData *serialized = [[NSUserDefaults standardUserDefaults] objectForKey:@"myKey"];
NSArray *myArray = [NSKeyedUnarchiver unarchiveObjectWithData:serialized];

您需要在NSCoding类中实现Occasion协议，并正确保存各种属性以使其正常工作。有关更多信息，请参阅Archives and Serializations Programming Guide。执行此操作不应超过几行代码。类似的东西：

- (void)encodeWithCoder:(NSCoder *)coder {
    [super encodeWithCoder:coder];

    [coder encodeObject:_title forKey:@"_title"];
    [coder encodeObject:_date forKey:@"_date"];
    [coder encodeObject:_imagePath forKey:@"_imagePath"];
}

- (id)initWithCoder:(NSCoder *)coder {
    self = [super initWithCoder:coder];

    _title = [[coder decodeObjectForKey:@"_title"] retain];
    _date = [[coder decodeObjectForKey:@"_date"] retain];
    _imagePath = [[coder decodeObjectForKey:@"_imagePath"] retain];

    return self;
}

Answer 2

NSUserDefaults用于用户首选项，而不是存储应用程序数据。使用CoreData或将对象序列化到文档目录中。您需要让您的类实现NSCoding协议才能生效。

1）在NSCoding

中实施Occasion.h

@interface Occasion : NSObject <NSCoding>

2）在Occasion.m

中实施协议

- (id)initWithCoder:(NSCoder *)aDecoder {

    if (self = [super init]) {

        self.title = [aDecoder decodeObjectForKey:@"title"];
        self.date = [aDecoder decodeObjectForKey:@"date"];
        self.imagePath = [aDecoder decodeObjectForKey:@"imagePath"];

    }            
    return self;
}

- (void)encodeWithCoder:(NSCoder *)aCoder {

    [aCoder encodeObject:title forKey:@"title"];
    [aCoder encodeObject:date forKey:@"date"];
    [aCoder encodeObject:imagePath forKey:@"imagePath"];
}

3）将数据存档到文档目录中的文件

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
                                    NSUserDomainMask, YES);
NSString *documentsPath = [paths objectAtIndex:0];
NSString *path= [documentsPath stringByAppendingPathComponent:@“occasions”];
[NSKeyedArchiver archiveRootObject:occasions toFile:path];

4）取消归档......

NSMutableArray *occasions = [NSKeyedUnarchiver unarchiveObjectWithFile:path];

Answer 3

您可以在NSCoding中实施Occasion。

然后使用[NSKeyedArchiver archivedDataWithRootObject:myArray]从数组中创建NSData对象。您可以将其设置为用户默认值。

将NSMutableArray保存到NSUserDefaults的最佳方法是什么？

3 个答案: