Question

我有这样定义的3个类：

class Device:
    Some method

class SSH:
    def connect(self,type):
    # code
    def execute(self,cmd):
    # code

class Netconf:
    def connect(self,type):
    # code
    def execute(self,cmd):
    # code

注意SSH和Netconf类具有相同的方法名称，但它们以不同的方式执行操作。我有类Device的实例，并希望访问这样的方法 -

d = Device()
d.connect('cli') # <-- This should call SSH method and subsequently
                 # d.execute(cmd) should call execute method from SSH class
                 # too.
d.connect('netconf') # <-- This should call Netconf method and subsequently
                     # d.execute(cmd) should call execute method from
                     # Netconf class too.

问题是 - 我该如何实现？我希望能够在Device类实例上使用SSH / Netconf类的方法＆＃39; d＆＃39;基于输入。

Answer 1

您可以通过存储在私有Device属性中连接的设备类型，然后通过添加自定义__getattr__()方法将大多数方法调用转发给它来实现此目的。这在connect()方法中有点棘手，因为这是定义了目标设备（而不是Device.__init__()初始化程序）。

我还将名为type的变量更改为kind，以避免与同名的内置模块发生冲突。

class Device(object):
    def connect(self, kind):
        if kind == 'cli':
            target = self._target = SSH()
        elif kind == 'netconf':
            target = self._target = Netconf()
        else:
            raise ValueError('Unknown device {!r}'.format(kind))
        return target.connect(kind)

    def __getattr__(self, name):
        return getattr(self._target, name)

class SSH(object):
    def connect(self, kind):
        print('SSH.connect called with kind {!r}'.format(kind))
    def execute(self, cmd):
        print('SSH.execute called with cmd {!r}'.format(cmd))

class Netconf(object):
    def connect(self, kind):
        print('Netconf.connect called with kind {!r}'.format(kind))
    def execute(self, cmd):
        print('Netconf.execute called with cmd {!r}'.format(cmd))

d = Device()
d.connect('cli')
d.execute('cmd1')
d.connect('netconf')
d.execute('cmd2')

输出：

SSH.connect called with kind 'cli'
SSH.execute called with cmd 'cmd1'
Netconf.connect called with kind 'netconf'
Netconf.execute called with cmd 'cmd2'

Answer 2

您应该实施Strategy Pattern。 connect()方法应该实例化适当的类（如果需要，从前一个detach()）并存储它，然后其他方法应该委托给存储的对象。

调用类方法

2 个答案: