时间戳

首页 > 解决方案 > 调用子类函数减少代码复制

python - 调用子类函数减少代码复制

问题描述

我希望通过在父类中使用公共代码来减少子类中的代码复制，但仍需要根据子类进行一些特定的处理。我知道从父母那里打电话给孩子是不好的。如何完成代码缩减？（或者我什至应该尝试？）

这是一个例子：

class Address:

    def __init__(self, street, city, postal_code):

        self._street = street
        self._city = city
        self._postal_code = self.valid_postal_code(postal_code)

    def valid_postal_code(self, postal_code):
        """ Returns a validated postal code """
        #
        # A big bunch of code common to all postal codes
        #

        if child == Usa:
            return Usa.valid_postal_code(postal_code)
        else:
            return Canada.valid_postal_code(postal_code)    

class Usa(Address):

    def valid_postal_code(self, postal_code):
        """ Returns a validated US zip code """
        # Must be 5 digits or 5 digits plus dash 4 digits
        if len(postal_code) != 5 and len(postal_code) != 10:
            raise Exception("Bad postal code")

        return postal_code


class Canada(Address):

    def valid_postal_code(self, postal_code):
        """ Returns a validates Canadian postal code """
        # Must be A#A #A#
        if len(postal_code) == 6:
            postal_code = postal_code[0:3] + " " + postal_code[3:3]
        if len(postal_code) != 7:
            raise Exception("Bad postal code")

        return postal_code.upper()

标签： pythonclassreduction

解决方案

有两种可能：

  • 让父代码包含公共部分，子代码包含细节
    • 父级必须返回中间结果

或者

  • 有两个父方法，其中一个是存根并被子方法覆盖
    • 父级将中间结果传递给存根

第二种方法看起来像：

class Address:

    def __init__(...):

    def valid_postal_code(self, postal_code):
        """ Returns a validated postal code """
        #
        # A big bunch of code common to all postal codes
        #
        return self._validate_postal_code(postal_code)

    def _validate_postal_code(self, postal_code):
        raise NotImplementedError


class Usa(Address):

    def _validate_postal_code(self, postal_code):
        """ Returns a validated US zip code """
        # Must be 5 digits or 5 digits plus dash 4 digits
        if len(postal_code) != 5 and len(postal_code) != 10:
            raise Exception("Bad postal code")
        return postal_code


class Canada(Address):

    def _validate_postal_code(self, postal_code):
        """ Returns a validates Canadian postal code """
        # Must be A#A #A#
        if len(postal_code) == 6:
            postal_code = postal_code[0:3] + " " + postal_code[3:3]
        if len(postal_code) != 7:
            raise Exception("Bad postal code")
        return postal_code.upper()

推荐阅读