Boost.Assign：将对象与map_list_of一起使用？

发布于 2024-12-06 05:21:38 字数 266 浏览 0 评论 0原文

使用带有 boost 的 C++。在 Boost.Assign 中，我可以将 new 运算符与 map_list_of 一起使用吗？

例如：

std::map<int, MyObject*> objects = boost::assign::map_list_of
       (1, new MyObject())(2, new MyObject())(3, new MyObject())

如果没有，还有其他方法吗？

原文

Using C++ with boost. In Boost.Assign can I use the new operator with map_list_of?

For example:

std::map<int, MyObject*> objects = boost::assign::map_list_of
       (1, new MyObject())(2, new MyObject())(3, new MyObject())

If not, is there another way to do it?

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[浮城] 2024-12-13 05:21:38

是的，它确实有效；调用 new 只是返回一个指向 MyObject 的指针，并且可以在该类型有效的任何地方使用它。但是对 new 的调用可能会引发异常，或者 MyObject 的构造函数可能会引发异常，这意味着堆分配的 MyObject 的整个映射将被泄漏。

如果您想要异常安全并且不必费心删除这些对象，则应该使用智能指针：

std::map<int, boost::shared_ptr<MyObject> > objects = boost::assign::map_list_of<int, boost::shared_ptr<MyObject> >
    (1, new MyObject())
    (2, new MyObject())
    (3, new MyObject());

It does work, yes; calling new just returns a pointer to MyObject, and it can be used anywhere that type is valid. HOWEVER the call to new might throw an exception, or MyObject's constructor might throw an exception, meaning your whole map of heap-allocated MyObjects will be leaked.

If you want exception safety as well as not having to bother deleting those objects, you should use a smart pointer instead:

std::map<int, boost::shared_ptr<MyObject> > objects = boost::assign::map_list_of<int, boost::shared_ptr<MyObject> >
    (1, new MyObject())
    (2, new MyObject())
    (3, new MyObject());

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心意如水 2024-12-13 05:21:38

看来是的。这与 VS2010 和 VS2010 编译得很好。提升1.47。

#include <boost\assign.hpp>
class MyObject{
public:
    MyObject(int i):m_i(i){}
private:
    int m_i;
};


int main (void)
{
    std::map<int, MyObject*> objects = boost::assign::map_list_of(1, new MyObject(1))(2, new MyObject(2))(3, new MyObject(3));
}

Seems yes. This compiles fine with VS2010 & boost 1.47.

#include <boost\assign.hpp>
class MyObject{
public:
    MyObject(int i):m_i(i){}
private:
    int m_i;
};


int main (void)
{
    std::map<int, MyObject*> objects = boost::assign::map_list_of(1, new MyObject(1))(2, new MyObject(2))(3, new MyObject(3));
}

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~没有更多了~