Pypy make_proxy

在 What PyPy can do for your objects — PyPy 2.1.0 documentation 看到 make_proxy 的範例：

from tputil import make_proxy

history = []
def recorder(operation):
    history.append(operation)
    return operation.delegate()

>>>> l = make_proxy(recorder, obj=[])
>>>> type(l)
list
>>>> l.append(3)
>>>> len(l)
1
>>>> len(history)
2

但實際卻會發生：

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/pypy/lib_pypy/tputil.py", line 29, in make_proxy
    tp = tproxy(type, perform)
TypeError: 'list' object could not be wrapped

參考 pypy 對 make_proxy 的測試，增加類別 A，並修改為

from tputil import make_proxy

class A(object):
  def append(self, item):
    pass

history = []
def recorder(operation):
    history.append(operation)
    return operation.delegate()

>>>> l = make_proxy(recorder, obj=[])
>>>> type(l)
<class '__main__.A'>
>>>> l.append(3)
>>>> len(history)
1
>>>> print history
[<ProxyOperation A.__getattribute__(<0x7f8f15887b50>, 'append')>]

這樣就可以了。make_proxy 是製造出一個代理物件，並且所有的操作都會呼叫 recorder 函式，範例裡，是呼叫 recorder 函式，把所有動作都紀錄到 history 裡。