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

Question

我已经定义了一个叫做场合的自定义对象如下：

#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; 

现在我有我要保存到NSUserDefaults的场合一个NSMutableArray。我知道这是不可能的，所以我想知道哪个是最简单的方法呢？如果序列化是答案，那么如何？因为我阅读了文档，但无法完全理解它的工作方式。

Answer 1

你应该使用类似NSKeyedArchiver到数组序列化为NSData，将它保存到NSUserDefaults，然后用NSKeyedUnarchiver以后反序列化：

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

//... 

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

您将需要实现你的Occasion的NSCoding协议类并正确保存各种属性以使其正确工作。欲了解更多信息，请参阅Archives and Serializations Programming Guide。这不应该超过几行代码。喜欢的东西：

- (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

你可以在Occasion实现NSCoding。

然后，您使用[NSKeyedArchiver archivedDataWithRootObject:myArray]从该数组创建一个NSData对象。你可以把它放到用户的默认值中。

Answer 3

NSUserDefaults用于用户偏好，不存储应用程序数据。使用CoreData或将对象序列化到文档目录中。你需要让你的班级实施NSCoding协议才能工作。

1）Occasion.h

@interface Occasion : NSObject <NSCoding> 

2实施NSCoding）在Occasion.m

- (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实现协议）存档在文件目录中的数据以一个文件

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

4 ）要取消存档...

NSMutableArray *occasions = [NSKeyedUnarchiver unarchiveObjectWithFile:path];