我正在编写一个测试应用程序来模拟 PIO 线，其中包含一个简单的 Python/Tk GUI 应用程序。该应用程序使用数字键 1 到 8 来模拟 PIO 引脚 1 到 8。按下按键 = PIO 高电平，释放按键 = PIO 低电平。我并不打算讨论应用程序的目的。我试图使用工厂方法创建一个按键回调函数，这个过程遇到了了一些问题。
以下是简化的代码示例：
from Tkinter import *
def cb_factory(numberic_key):
def cb(self, event, key=numberic_key):
bit_val = 1 << numberic_key - 1
if int(event.type) == 2 and not (bit_val & self.bitfield):
self.bitfield |= bit_val
self.message("Key %d Down" % key)
elif int(event.type) == 3 and (bit_val & self.bitfield):
self.bitfield &= (~bit_val & 0xFF)
self.message("Key %d Up" % key)
else:
# Key repeat
return
print(hex(self.bitfield))
self.display_bitfield()
return cb
class App(Frame):
cb1 = cb_factory(1)
cb2 = cb_factory(2)
cb3 = cb_factory(3)
cb4 = cb_factory(4)
cb5 = cb_factory(5)
cb6 = cb_factory(6)
cb7 = cb_factory(7)
cb8 = cb_factory(8)
def __init__(self, parent):
"Init"
self.parent = parent
self.bitfield = 0x00
Frame.__init__(self, parent)
self.messages = StringVar()
self.messages.set("Initialised")
Label(parent, bd=1, relief=SUNKEN, anchor=W,
textvariable=self.messages, text="Testing").pack(fill=X)
self.bf_label = StringVar()
self.bf_label.set("0 0 0 0 0 0 0 0")
Label(parent, bd=1, relief=SUNKEN, anchor=W,
textvariable=self.bf_label, text="Testing").pack(fill=X)
# This doesn't work! Get a traceback saying 'cb' expected 2 arguments
# but only got 1?
#
# for x in xrange(1, 9):
# cb = self.cb_factory(x)
# self.parent.bind("<KeyPress-%d>" % x, cb)
# self.parent.bind("<KeyRelease-%d>" % x, cb)
self.parent.bind("<KeyPress-1>", self.cb1)
self.parent.bind("<KeyRelease-1>", self.cb1)
self.parent.bind("<KeyPress-2>", self.cb2)
self.parent.bind("<KeyRelease-2>", self.cb2)
self.parent.bind("<KeyPress-3>", self.cb3)
self.parent.bind("<KeyRelease-3>", self.cb3)
self.parent.bind("<KeyPress-4>", self.cb4)
self.parent.bind("<KeyRelease-4>", self.cb4)
self.parent.bind("<KeyPress-5>", self.cb5)
self.parent.bind("<KeyRelease-5>", self.cb5)
self.parent.bind("<KeyPress-6>", self.cb6)
self.parent.bind("<KeyRelease-6>", self.cb6)
self.parent.bind("<KeyPress-7>", self.cb7)
self.parent.bind("<KeyRelease-7>", self.cb7)
self.parent.bind("<KeyPress-8>", self.cb8)
self.parent.bind("<KeyRelease-8>", self.cb8)
def display_bitfield(self):
bin_lst = []
for x in xrange(8):
bit = 1 << x
if bit & self.bitfield:
bin_lst.append("1")
else:
bin_lst.append("0")
bin_lst.reverse()
bin_str = " ".join(bin_lst)
self.bf_label.set(bin_str)
def message(self, msg_txt):
"set"
self.messages.set(msg_txt)
def cb_factory(self, numberic_key):
def cb(self, event, key=numberic_key):
bit_val = 1 << numberic_key - 1
if int(event.type) == 2:
self.bitfield |= bit_val
self.message("Key %d Down" % key)
else:
self.bitfield &= (~bit_val & 0xFF)
self.message("Key %d Up" % key)
print(hex(self.bitfield))
self.display_bitfield()
return cb
##########################################################################
if __name__ == "__main__":
root = Tk()
root.title("PIO Test")
theApp = App(root)
root.mainloop()
我最终让方法工厂工作起来创建回调函数，但我并不满意。因此，我的问题是，你能否有一个类方法工厂，它将按照我尝试的方式（请参阅注释掉的代码和 App 类方法 cb_factory()）生成类方法？
注意：我知道这个应用程序一次只能让你按住 4 个键，但这对我来说已经足够了。
- 解决方案
方法一：传递 self 参数
你可以在工厂函数中传递 self 参数。修改后的代码如下：
def cb_factory(self, numberic_key):
def cb(event, key=numberic_key):
bit_val = 1 << numberic_key - 1
if int(event.type) == 2 and not (bit_val & self.bitfield):
self.bitfield |= bit_val
self.message("Key %d Down" % key)
elif int(event.type) == 3 and (bit_val & self.bitfield):
self.bitfield &= (~bit_val & 0xFF)
self.message("Key %d Up" % key)
else:
# Key repeat
return
print(hex(self.bitfield))
self.display_bitfield()
return cb
方法二：使用 functools.partial
你也可以使用 functools.partial 来创建类方法工厂。修改后的代码如下：
from functools import partial
def cb_factory(self, numberic_key):
cb = partial(self.key_action, key=numberic_key)
return cb
def key_action(self, event, key):
bit_val = 1 << key - 1
if int(event.type) == 2 and not (bit_val & self.bitfield):
self.bitfield |= bit_val
self.message("Key %d Down" % key)
elif int(event.type) == 3 and (bit_val & self.bitfield):
self.bitfield &= (~bit_val & 0xFF)
self.message("Key %d Up" % key)
else:
# Key repeat
return
print(hex(self.bitfield))
self.display_bitfield()
