过去，判断一个字典对象的合法性，采用了下面的方案。有一个很大的缺点就是，数据非法时，想要定位到哪个字段出了问题，这事并不轻松。

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+ (BOOL)isValidDic:(NSDictionary *)dic
{
    if (![super isValidDic:dic]
        || !DIC_HAS_STRING(dic, SYNC_USER_UID)
        || !DIC_HAS_STRING(dic, SYNC_CONTENT)
        || !DIC_HAS_NUMBER(dic, SYNC_CREATE_TIME)
        || !DIC_HAS_ARRAY(dic, SYNC_COMMENTS)
        || !DIC_HAS_ARRAY(dic, SYNC_FAVORS)
        || !DIC_HAS_ARRAY(dic, SYNC_VISITORS)
        || !DIC_HAS_NUMBER(dic, SYNC_COMMENT_NUM)
        || !DIC_HAS_NUMBER(dic, SYNC_FAVOR_NUM)
        || !DIC_HAS_NUMBER(dic, SYNC_VISITOR_NUM)
        || !DIC_HAS_NUMBER(dic, SYNC_IS_HIDE_IN_SQUARE)
        || !DIC_HAS_NUMBER(dic, SYNC_FAVORED)
        || !DIC_HAS_ARRAY(dic, SYNC_PHOTOS)
        || ![UserBasicInfo isValidDic:dic[SYNC_USER_INFO]]
        )
    {
        return NO;
    }
    
    return YES;
}
优化方案

这个思路不限于 Objective-C

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+ (BOOL)isValidDic:(NSDictionary *)dic
{
    NSDictionary *checkMap = @{@"super": ^{return [super isValidDic:dic];},
                               SYNC_USER_UID: ^{return DIC_HAS_STRING(dic, SYNC_USER_UID);},
                               SYNC_CONTENT: ^{return DIC_HAS_STRING(dic, SYNC_CONTENT);},
                               SYNC_CREATE_TIME: ^{return DIC_HAS_NUMBER(dic, SYNC_CREATE_TIME);},
                               SYNC_COMMENTS: ^{return DIC_HAS_ARRAY(dic, SYNC_COMMENTS);},
                               SYNC_FAVORS: ^{return DIC_HAS_ARRAY(dic, SYNC_FAVORS);},
                               SYNC_VISITORS: ^{return DIC_HAS_ARRAY(dic, SYNC_VISITORS);},
                               SYNC_COMMENT_NUM: ^{return DIC_HAS_NUMBER(dic, SYNC_COMMENT_NUM);},
                               SYNC_FAVOR_NUM: ^{return DIC_HAS_NUMBER(dic, SYNC_FAVOR_NUM);},
                               SYNC_VISITOR_NUM: ^{return DIC_HAS_NUMBER(dic, SYNC_VISITOR_NUM);},
                               SYNC_IS_HIDE_IN_SQUARE: ^{return DIC_HAS_NUMBER(dic, SYNC_IS_HIDE_IN_SQUARE);},
                               SYNC_FAVORED: ^{return DIC_HAS_NUMBER(dic, SYNC_FAVORED);},
                               SYNC_PHOTOS: ^{return DIC_HAS_ARRAY(dic, SYNC_PHOTOS);},
                               SYNC_USER_INFO: ^{return [UserBasicInfo isValidDic:dic[SYNC_USER_INFO]];}
                            };
    for (NSString *key in [checkMap allKeys])
    {
        BOOL (^handler)() = checkMap[key];
        BOOL ret = handler();
        if(!ret)
        {
            CLog(@"%@ %@: invalid: %@", NSStringFromClass([self class]), NSStringFromSelector(_cmd), key);
            return NO;
        }
    }
    
    return YES;
}