是否可以查询 PyQt4 QObject 以确定底层 C++实例已被破坏？

Question

destroyed() 信号可以被 QObject 捕获，但我想简单地测试 Python 对象是否仍然引用有效的 C++ Qt 对象。有没有直接这样做的方法？

Answer 1

如果导入 sip 模块，则可以调用其 .isdeleted 函数。

import sip
from PyQt4.QtCore import QObject

q = QObject()
sip.isdeleted(q)
False

sip.delete(q)
q
<PyQt4.QtCore.QObject object at 0x017CCA98>

q.isdeleted(q)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: underlying C/C++ object has been deleted

Answer 2

您可以使用Python标准库中的WeakRef类。它看起来像：

import weakref

q = QObject()
w = weakref.ref(q)

if w() is not None: # Remember the parentheses!
    print('The QObject is still alive.')
else:
    print('Looks like the QObject died.')