Qt Raw vs std :: shared_ptr [英] Qt raw vs std::shared_ptr

问题描述

我注意到在QT中用shared_ptr替换原始指针时，我的代码不再起作用。
例如，如果不是

I noticed that when substituting raw pointers with shared_ptr in QT, my code does not work anymore. For example, if instead of

 QTreeWidgetItem* vItem(new QTreeWidgetItem(ItemTitle));

我使用

 std::shared_ptr<QTreeWidgetItem> vItem(new QTreeWidgetItem(ItemTitle));

然后，程序崩溃或什么也没做（即使我使用.get（）函数从我的代码后面的共享指针中获取
原始指针）。有人知道是什么原因吗？

then, either the program crashes or nothing is done (even if I use the .get() function to get the raw pointer from the shared one later in my code). Does anybody knows what could be the cause?

推荐答案

在Qt模型项中使用共享指针会导致所有权冲突： QTreeWidget 获取您传递给它的任何 QTreeWidgetItem 的所有权。 std :: shared_ptr 也拥有它的物品。两者都假定他们可以自己删除该项目，没有其他人可以将其删除。

Using shared pointer with Qt model items causes an ownership conflict: QTreeWidget takes ownership of any QTreeWidgetItem you pass to it. std::shared_ptr also owns its item. Both assume they can delete the item themselves and that nobody else will delete it behind their back.

在这种情况下，Qt拥有指针的所有权（另一个示例：parent） QObject 拥有其子代的所有权），则不能使用 std :: shared_ptr / QSharedPointer 同时。 std :: shared_ptr 仅在使用 std :: shared_ptr 和 std :: weak_ptr时才能很好地工作专门用于保存指向该特定对象的指针。

In such situations, where Qt takes ownership of the pointers (other example: parent QObject taking ownership of its children), one cannot use std::shared_ptr/QSharedPointer at the same time. std::shared_ptr only works well when using std::shared_ptr and std::weak_ptr exclusively to hold pointers to that particular object.

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