objective-c – check id isKindOfType CFType

我正在实现dynamic core data attributes并且在ExtendedManagedObject的willSave方法中我想检查id值是否为CFType以将其存储到plist文件中.

如果我试图保存为UIImage,那就不是免费的CF桥接(apple docs),我收到一个错误：

2011-11-17 17：16：25.294 [490：707]保存扩展数据时出错：属性列表对格式无效(属性列表不能包含’CFType’类型的对象)

我可以用某种方法检查它,或者我必须自己实现(只是来自docs的isKindOfClass)？

我不想在NSManagedObject子类中实现访问器,我不知道我将从实体属性中获得多少URL.问题是关于运行时的动态扩展属性.

- (void)willSave
{
NSDictionary *changes = [self valueForKey:@"extendedChanges"];
if (changes!=nil) {
    // merge changes into snapshot
    NSMutableDictionary *dict = [[self extendedSnapshot] mutableCopy];
    NSEnumerator *e = [changes keyEnumerator];
    NSString *key;
    while (key=[e nextObject]) {
        id value = [changes objectForKey:key];



        if (value==[NSNull null])
            [dict removeObjectForKey:key];
        else if (#ugly and I'm not shure is thread safe **else if ([value isKindOfClass:[NSArray class]] || [value isKindOfClass:[NSDictionary class]] || [value isKindOfClass:[NSDate class]] || [value isKindOfClass:[NSData class]] || [value isKindOfClass:[NSString class]] || [value isKindOfClass:[NSNumber class]])**)
            [dict setObject:value forKey:key];
    }

    // archive as binary plist
    NSData *data = nil;
    if ([dict count]>0) {
        NSString *error=nil;
        data = [NSPropertyListSerialization dataFromPropertyList:dict 
                                                          format:NSPropertyListBinaryFormat_v1_0 errorDescription:&error];
        if (error!=nil) {
            NSLog(@"Error saving extended data: %@",error);
            [error release];
        }
    }
    [dict release];
    [self setPrimitiveValue:data forKey:@"extendedData"];
}
[super willSave];
}