在自定义类的子类上使用NSCoding

Question

我使用NSCoding归档/取消归档自定义类作为数据持久性的方法.如果对象是NSObject的子类,它可以正常工作,但我也有自定义对象的子类.我是否需要更改initWithCoder:方法以及encodeWithCoder？现在,特定于子类的属性编码/解码很好,但子类继承自超类的属性不是.有什么想法吗？这是基本结构:

@interface NewsItem : NSObject <NSCoding, NSCopying> {
//properties for the super class here
}

@implementation NewsItem
- (void)encodeWithCoder:(NSCoder *)coder {
    [coder encodeObject:itemName forKey:kItemNameKey];
//etc etc
}

- (id)initWithCoder:(NSCoder *)coder {
    if ( (self = [super init]) )
    {
        self.itemName = [coder decodeObjectForKey:kItemNameKey];
//etc etc
    }
    return self;
}

-(id)copyWithZone:(NSZone *)zone {
    NewsItem *copy = [[[self class] allocWithZone: zone] init];
    copy.itemName = [[self.itemName copy] autorelease];
//etc etc
    return copy;
}

和子类:

@interface File : NewsItem {
    NSString *fileSizeString;
//etc etc
}

@implementation File
- (void)encodeWithCoder:(NSCoder *)coder {
    [super encodeWithCoder:coder]; //added this, but didn't seem to make a difference
    [coder encodeObject:fileSizeString forKey:kFileSizeStringKey];
//etc etc

}

- (id)initWithCoder:(NSCoder *)coder {
    if ( (self = [super init]) )
    {
        self.fileSizeString = [coder decodeObjectForKey:kFileSizeStringKey];
//etc etc
    }
    return self;
}

-(id)copyWithZone:(NSZone *)zone {
    File *copy = (File *)[super copyWithZone:zone];
    copy.fileSizeString = [[self.fileSizeString copy] autorelease];
//etc etc
    return copy;
}

Answer 1

在里面File的initWithCoder:方法

if ( (self = [super init]) )

应该

if ( (self = [super initWithCoder:coder]) )