objc実装クラス変数

HTTPRiotソースから学びました.mergedOptionsという方法を見て、RUBYのことを思い出した.
 

@implementation HRRestModel
//       ，          
static NSMutableDictionary *attributes;
 
+ (void)initialize {    
    if(!attributes)
        attributes = [[NSMutableDictionary alloc] init];
}
 
//              ，      
+ (NSMutableDictionary *)classAttributes {
    NSString *className = NSStringFromClass([self class]);
 
    NSMutableDictionary *newDict;
    NSMutableDictionary *dict = [attributes objectForKey:className];
 
    if(dict) {
        return dict;
    } else {
        newDict = [NSMutableDictionary dictionaryWithObject:[NSNumber numberWithInt:HRDataFormatJSON] forKey:@"format"];
        [attributes setObject:newDict forKey:className];
    }
 
    return newDict;
}
 
//      
+ (void)setAttributeValue:(id)attr forKey:(NSString *)key {
    [[self classAttributes] setObject:attr forKey:key];
}