重构的设计模式答案

【问题标题】：Design pattern for refactoring重构的设计模式
【发布时间】：2015-05-28 13:51:39
【问题描述】：

我有这三个函数，我觉得重复所有相同的代码很难看，这根本不是 DRY。同时，我不确定如何重构这些函数以保持清晰的表达。有什么推荐的吗？

谢谢

def download_loc(instance, filename):
    username = instance.username_or_anonymous()
    slug = instance.slug
    filename_with_timestamp = filename_timestamped(instance, filename)
    return "%s/%s/stl/%s" % (username, slug, filename_with_timestamp)

def preview_loc(instance, filename):
    username = instance.username_or_anonymous()
    slug = instance.slug
    filename_with_timestamp = filename_timestamped(instance, filename)
    return "%s/%s/preview/%s" % (username, slug, filename_with_timestamp)

def screenshot_loc(instance, filename):
    username = instance.username_or_anonymous()
    slug = instance.slug
    filename_with_timestamp = filename_timestamped(instance, filename)
    return "%s/%s/screenshot/%s" % (username, slug, filename_with_timestamp)

【问题讨论】：

您将类型（stl、预览和屏幕截图）设为另一个参数并具有一个功能
看相同的，看不同的，各自封装。

标签： python design-patterns refactoring

【解决方案1】：

引入第三个函数，它将类型名称作为参数。就我个人而言，我只会调用该函数，但如果它是从很多地方调用的，那么包装它是有价值的。

def loc(instance, filename, typename):
    username = instance.username_or_anonymous()
    slug = instance.slug
    filename_with_timestamp = filename_timestamped(instance, filename)
    return "{}/{}/{}/{}".format(username, slug, typename, filename_with_timestamp)

def download_loc(instance, filename):
    return loc(instance, filename, "stl")

def preview_loc(instance, filename):
    return loc(instance, filename, "preview")

def screenshot_loc(instance, filename):
    return loc(instance, filename, "screenshot")

【讨论】：

请注意，% 运算符已弃用，取而代之的是 str.format。