我发现创建在某些逻辑中包装参数化对象属性的“方法工厂函数”很有用。
例如:
"""Fishing for answers.
>>> one().number_fisher()
'one fish'
>>> one().colour_fisher()
'red fish'
>>> two().number_fisher()
'two fish'
>>> two().colour_fisher()
'blue fish'
"""
class one(object):
def number(self):
return 'one'
def colour(self):
return 'red'
def _make_fisher(sea):
def fisher(self):
return '{0} fish'.format(getattr(self, sea)())
return fisher
number_fisher = _make_fisher('number')
colour_fisher = _make_fisher('colour')
class two(one):
def number(self):
return 'two'
def colour(self):
return 'blue'
是否有必要将属性make_fisher
作为字符串传递,还是有更好的方法来做到这一点?
如果我传递并使用一个实际属性,这将破坏多态性,因为 的实例two
仍将使用对属性对象的相同引用。
IE
diff --git a/fishery.py b/fishery.py
index 840e85d..b98cf72 100644
--- a/fishery.py
+++ b/fishery.py
@@ -4,10 +4,12 @@
'one fish'
>>> one().colour_fisher()
'red fish'
+
+This version does not implement polymorphism, and so this happens:
>>> two().number_fisher()
-'two fish'
+'one fish'
>>> two().colour_fisher()
-'blue fish'
+'red fish'
"""
@@ -18,10 +20,10 @@ class one(object):
return 'red'
def _make_fisher(sea):
def fisher(self):
- return '{0} fish'.format(getattr(self, sea)())
+ return '{0} fish'.format(sea(self))
return fisher
- number_fisher = _make_fisher('number')
- colour_fisher = _make_fisher('colour')
+ number_fisher = _make_fisher(number)
+ colour_fisher = _make_fisher(colour)
class two(one):
def number(self):
必须使用字符串来引用属性似乎有点弱,但我没有看到另一种方法来做到这一点。在那儿?