一、背景

• 大量的if … elif…代码非常难看，也很难维护。
• 扩展不太方便

二、优化方案

• 以下栗子展示不同的角色获取折扣信息。

1、正常写法

def discount_algorithm(user_role):
    if user_role == 'admin':
        discount = 0.1
        return discount
    elif user_role == 'msp':
        discount = 0.3
        return discount
    elif user_role == 'tenant':
        discount = 0.5
        return discount
    elif user_role == 'number':
        discount = 0.7
        return discount
    else:
        discount = 1
        return discount


user_role = 'admin'
discount = discount_algorithm(user_role)

2、使用字典

def get_admin_discount():
    pass


def get_msp_discount():
    pass


def get_tenant_discount():
    pass


def get_number_discount():
    pass


def get_default_discount():
    pass


user_discount_map = {
    'admin': get_admin_discount(),
    'msp': get_msp_discount(),
    'tenant': get_tenant_discount(),
    'number': get_number_discount(),
    'default': get_default_discount(),
}

discount = user_discount_map[user_role]

3、使用反射

class DiscountAlgorithm():
    def get_admin_discount(self):
        pass

    def get_msp_discount(self):
        pass

    def get_tenant_discount(self):
        pass

    def get_number_discount(self):
        pass

    def get_default_discount(self):
        pass

    def get_discount(self, user_role):
        return getattr(self, user_role)()


DiscountAlgorithm().get_discount('get_msp_discount')

三、小结

• 正常写法适合确定的只有2-3个if条件的情况
• 字典适合代码量比较小的
• 反射适合代码量比较多的