随机消失的结构
我创建了一个 Objective-C 类来使用 libpq 与 PostgreSQL 交互。它基本上可以工作，但我有一个小问题 - 连接似乎随机消失。
此类设置为在打开窗口时打开连接，并在窗口关闭之前关闭该连接。在窗口的初始化代码中，我打开连接并监听通知，以便可以使用 PQfinnish() 关闭连接。
现在，如果我打开该窗口，我可以运行任意数量的查询。但如果我关闭它并再次打开它，我会收到 EXC_BAD_ACCESS 错误。该错误似乎在 libpq 内部，但我不知道我做错了什么 - 没有可遵循的示例，这使得遵循模式变得有点困难。
我相信连接对象似乎有问题，但我无法准确找出问题所在，因为所有诊断函数似乎都返回正确的值。
Postgresql 8.0，运行在最新的 OS X、最新的 Xcode 和目标为 10.5 的项目上
I've created a Objective-C class to interface with PostgreSQL using libpq. It mostly works but I have one small problem - the connection seems to disappear randomly.
This class is set to open a connection when a window is opened and close that connection before the window closes. On the init code of the window I open the connection and I listen to notifications so I can close the connection with PQfinnish().
Now if I open that window, I can run as many queries as I want. But if I close it and open it again I get an EXC_BAD_ACCESS error. The error seems to be inside libpq but I've no idea what I'm doing wrong - there's no examples to follow which makes it a bit harder to follow patterns.
I believe there seems to be a problem with the connection object but I can't find out exactly what as all diagnostic functions seem to be returning the right values.
Postgresql 8.0, running on latest OS X, latest Xcode and project targeted at 10.5
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找到答案：
崩溃的代码是从通知触发的事件中调用的。崩溃是因为我在关闭窗口时没有从通知中心取消注册该类。
我现在从中心取消注册该课程，一切正常。
但不知道为什么问题会反映在连接对象上。
Found the answer:
The code that crashed was called from an event that was fired from a notification. The crash came because I wasn't unregistering that class from the notification centre when closing the window.
I now unregister that class from the centre and all works well.
No idea why the problem reflected itself on the connection object, though.