objc 实现类变量

从HTTPRiot 源码学习而来。
看到 mergedOptions 这个方法还真想起RUBY的好。

 

@implementation HRRestModel
// 全局静态变量，类变量就是用这个存储
static NSMutableDictionary *attributes;
 
+ (void)initialize {    
    if(!attributes)
        attributes = [[NSMutableDictionary alloc] init];
}
 
// 防止继承的类使用相同的变量，很漂亮的代码
+ (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;
}
 
// 设置类变量
+ (void)setAttributeValue:(id)attr forKey:(NSString *)key {
    [[self classAttributes] setObject:attr forKey:key];
}