管理（和重命名）类组成的实例变量 [英] Managing (and renaming) instance variables of class compositions

问题描述

我想进行类组合，以使组成类的实例变量成为组合的实例变量，但名称经过调整。

I would like to make a class composition so that the instance variables of the composing classes become instance variables of the composition but with adjusted names.

此应用程序是在matplotlib中定义用于绘制的新对象。一个例子是我想拥有一个 drawMyArrow 函数，该函数为其头部，尾部和弧线绘制一个可能具有不同颜色（和其他规格）的箭头。我希望能够通过 drawMyArrow 中的关键字参数传递有关头，尾和弧的各种规格。我以前没有使用过类，但是在网上阅读了此书后，我相信解决我的问题的最好方法是定义一个类 MyArrow 一些类 ArrowHead 和 ArrowArc 。

The application for this is in defining new objects for drawing in matplotlib. One example is that I would like to have a function drawMyArrow that draws an arrow with possibly different colors (and other specifications) for its head, tail, and arc. I would like to be able to pass various specifications for the head, tail, and arc via keyword arguments in drawMyArrow. I haven't worked with classes before, but reading up on this online, I believe that the best way to solve my problem is to define a class MyArrow that is a composition of some classes ArrowHead and ArrowArc.

问题，请考虑一个简单的玩具示例。让我们定义一个类 Room ，它是由 wall ， window 和门。

To illustrate my problem, consider a simple toy example. Let's define a class Room that is a composition of the classes wall, window, and door.

class Door:
    def __init__(self, color='white', height=2.3, width=1.0):
        self.color = color
        self.height = height
        self.width = width

class Window:
    def __init__(self, color='white', height=1.0, width=0.8):
        self.color = color
        self.height = height
        self.width = width

class Wall:
    def __init__(self, color='white', height=2.5, width=4.0):
        self.color = color
        self.height = height
        self.width = width

class Room:
    def __init__(self):
        self.door = Door()
        self.window = Window()
        self.wall = Wall()

门， Window 和 Wall 的实例变量code>是颜色，高度，宽度。我希望 Room 具有实例变量 doorcolor ， windowcolor ，壁彩，门高， windowheight 等。我可以将所有九个实例变量明确添加到 Room 并定义 set 和 get 为他们提供的功能。但是，如果我以后决定将更多实例变量添加到 Door ， Window 或 Wall 我也总是需要再次编辑 Room 的代码。有没有办法编写 Room 的代码，以便它自动采用（并重命名）其组件类中的实例变量？

The instance variables of Door, Window, and Wall are color, height, width. I would like Room to have instance variables doorcolor, windowcolor, wallcolor, doorheight, windowheight, etc. I could add all nine instance variables to Room explicitly and define set and get functions for them. But if I later decide to add more instance variables to Door, Window, or Wall I would always need to edit the code for Room again too. Is there a way to code Room so that it adopts (and renames) the instance variables from its component classes automatically?

推荐答案

您正在使用合成-无需为您的成员复制访问器。您可以轻松地通过组成的成员通过 访问属性：

You are using composition - no need to replicate accessors for your members. You can easily access the attributes through your composed members:

r = Room()
print( r.window.color ) # to print the windows color only

---

您可能会从零件的基类中受益，并为房间的 __ init __（..）获利类：

---

You might profit from a base class for your "parts" and a changed __init__(..) for your Room class though:

class Thing:
    """Base class handling init including a name and __str__ and __repr__."""
    def __init__(self, name, color, height, width):
        self.name = name
        self.color = color
        self.height = height
        self.width = width

    def __str__(self):
        return repr(self)

    def __repr__(self):
        return str([self.name, self.color, self.height, self.width])

class Door(Thing):
    def __init__(self, color='white', height=2.3, width=1.0):
        super(self.__class__, self).__init__(self.__class__.__name__, color, height, width)

class Window(Thing):
    def __init__(self, color='white', height=2.3, width=1.0):
        super(self.__class__, self).__init__(self.__class__.__name__, color, height, width)

class Wall(Thing):
    def __init__(self, color='white', height=2.5, width=4.0):
        super(self.__class__, self).__init__(self.__class__.__name__, color, height, width) 

class Room:
    def __init__(self,*, door=None, window=None, wall=None): # named params only
        self.door = door or Door()           # default to booring Door if none provided
        self.window = window or Window()     # same for Window
        self.wall = wall or Wall()           # same for Wall

    def __str__(self):
        return str([self.door,self.window,self.wall])

创建对象并打印它们：

r = Room()
r2 = Room(window=Window("yellow"))

print(r)
print(r2)

r3 = Room( window=Window("green",0.5,0.5), door=Door("black",5,5), 
           wall=Wall("unicorncolored",5,5) )

print(r3)

输出：

# r - the cheap Room - using default-ing Things
[['Door', 'white', 2.3, 1.0], ['Window', 'white', 2.3, 1.0], ['Wall', 'white', 2.5, 4.0]]

# r2 - with a custom yellow Window
[['Door', 'white', 2.3, 1.0], ['Window', 'yellow', 2.3, 1.0], ['Wall', 'white', 2.5, 4.0]]

# r3 - all custom - 
[['Door', 'black', 5, 5], ['Window', 'green', 0.5, 0.5], ['Wall', 'unicorncolored', 5, 5]]

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