Runtime set init value.

CheckEntity

/*
// DEMO
int main(int argc, const char *argv[]) {
    @autoreleasepool {
        // JSON到Entity
        UserEntity *userEntity = [UserEntity new];
        // 检查属性，设置默认值。
        checkEntity(userEntity);

        NSLog(@"%@", userEntity);
    }
    return 0;
}
*/

/**
* 解析Property的Attributed字符串
*/
static const char *getPropertyType(objc_property_t property) {
    const char *attributes = property_getAttributes(property);
    char buffer[1 + strlen(attributes)];
    strcpy(buffer, attributes);
    char *state = buffer, *attribute;
    while ((attribute = strsep(&state, ",")) != NULL) {
        if (attribute[0] == 'T' && attribute[1] != '@') {
            // 利用NSData复制一份字符串
            return (const char *) [[NSData dataWithBytes:(attribute + 1) length:strlen(attribute) - 1] bytes];
        } else if (attribute[0] == 'T' && attribute[1] == '@' && strlen(attribute) == 2) {
            return "id";
        } else if (attribute[0] == 'T' && attribute[1] == '@') {
            return (const char *) [[NSData dataWithBytes:(attribute + 3) length:strlen(attribute) - 4] bytes];
        }
    }
    return "";
}

/**
* 给对象的属性设置默认值
*/
void checkEntity(NSObject *object) {
    // 类型常量
    static const char *CLASS_NAME_NSSTRING;
    static const char *CLASS_NAME_NSNUMBER;
    static const char *CLASS_NAME_NSARRAY;

    // 初始化类型常量
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        CLASS_NAME_NSSTRING =  NSStringFromClass([NSString class]).UTF8String;
        CLASS_NAME_NSNUMBER = NSStringFromClass([NSNumber class]).UTF8String;
        CLASS_NAME_NSARRAY = NSStringFromClass([NSArray class]).UTF8String;
    });

    @try {
        unsigned int outCount, i;
        objc_property_t *properties = class_copyPropertyList([object class], &outCount);

        for (i = 0; i < outCount; i++) {
            objc_property_t property = properties[i];
            NSString *propertyName = [NSString stringWithUTF8String:property_getName(property)];
            id propertyValue = [object valueForKey:propertyName];

            // 值为空，才设置默认值
            if (!propertyValue) {
                // NSString
                if (strncmp(CLASS_NAME_NSSTRING, getPropertyType(property), strlen(CLASS_NAME_NSSTRING)) == 0) {
                    [object setValue:@"str" forKey:propertyName];
                }

                // NSNumber
                if (strncmp(CLASS_NAME_NSNUMBER, getPropertyType(property), strlen(CLASS_NAME_NSNUMBER)) == 0) {
                    [object setValue:@100 forKey:propertyName];
                }

                // NSArray
                if (strncmp(CLASS_NAME_NSARRAY, getPropertyType(property), strlen(CLASS_NAME_NSARRAY)) == 0) {
                    [object setValue:@[@"item"] forKey:propertyName];
                }
            }
        }

        free(properties);
    } @catch (NSException *exception) {
        NSLog(@"Check Entity Exception: %@", [exception description]);
    }
}