'@reify'做什么以及何时使用？

I saw it in the Pyramid tutorial for UX design. I couldn't make out much what this decorator is all about.

我在用于UX设计的金字塔教程中看到了它。我无法弄清楚这个装饰器是什么。

Sample code where I saw its usage.

我看到其用法的示例代码。

def __init__(self, request):
    self.request = request
    renderer = get_renderer("templates/global_layout.pt")
    self.global_template = renderer.implementation().macros['layout']

@reify
def company_name(self):
    return COMPANY

@reify
def site_menu(self):
    new_menu = SITE_MENU[:]
    url = self.request.url
    for menu in new_menu:
        if menu['title'] == 'Home':
            menu['current'] = url.endswith('/')
        else:
            menu['current'] = url.endswith(menu['href'])
    return new_menu

@view_config(renderer="templates/index.pt")
def index_view(self):
    return {"page_title": "Home"}

@view_config(renderer="templates/about.pt", name="about.html")
def about_view(self):
    return {"page_title": "About"}

2 个解决方案

#1

From the source code documentation:

从源代码文档:

""" Put the result of a method which uses this (non-data) descriptor decorator in the instance dict after the first call, effectively replacing the decorator with an instance variable."""

msgstr“”“在第一次调用后,在实例dict中放置一个使用此(非数据)描述符装饰器的方法的结果,有效地用实例变量替换装饰器。”“

A description from from the fuzzy notepad blog sums it up nicely.

来自模糊记事本博客的描述很好地总结了它。

It acts like @property, except that the function is only ever called once; after that, the value is cached as a regular attribute. This gives you lazy attribute creation on objects that are meant to be immutable.

它的作用类似于@property,只是该函数只被调用一次;之后,该值将缓存为常规属性。这使您可以在对象上创建惰性属性,这些对象应该是不可变的。

So in the code you posted, site_menu can be accesses like a cached property.

因此,在您发布的代码中,site_menu可以像缓存属性一样进行访问。

#2

According to the doc string (source):

根据doc字符串(来源):

""" Put the result of a method which uses this (non-data)
descriptor decorator in the instance dict after the first call,
effectively replacing the decorator with an instance variable."""

#1