在循环中创建新的指针对象 [英] Creating new pointer object in loop

问题描述

说我做这样的事情

for(int i = 0; i < 10; i++)
{
    //create a pointer object using new
    //use the object
}

在循环中使用指针对象后是否需要删除指针对象?我在想，如果我不删除它，它会不断创建一个新对象 10 次，然后该对象就挂在那里，吃资源.

Do I need to delete the pointer object after using it in the loop? I was thinking like, if I didn't delete it, it will keep creating a new object for 10 times and the object just hang in there after that, eating resources.

推荐答案

是的，对于每一个new，都需要有一个对应的delete.(并且每个 new[] 都有一个 delete[].)

Yes, for every new there needs to be a corresponding delete. (And a delete[] for every new[].)

然而，C++ 的方式是尽可能避免动态存储，而是使用局部、自动变量:

However, the C++ way would be to avoid dynamic storage as much as possible and rather employ local, automatic variables:

for(int i = 0; i < 10; ++i)
{
    some_class object;
    //use object
} // object gets destroyed here automatically 

如果您需要动态分配该对象(我对此表示怀疑，但确实存在这种情况)，那么使用智能指针.一个智能指针会为你执行 delete，无论你以何种方式离开它所属的范围:

If you need to allocate that object dynamically (which I doubt, but there are such cases), then use a smart pointer. A smart pointer will execute the delete for you, no matter which way you leave the scope it belongs to:

for(int i = 0; i < 10; ++i)
{
    smart_ptr<some_class> object(new some_class());
    //use object
} // object gets destroyed here automatically 

当前的标准只知道一个名为 std::auto_ptr 的智能指针，在这种情况下它可以满足您的需求.下一个标准将带来更多，其中替换了 std::auto_ptr，名为 std::unique_ptr，还有一个具有共享所有权语义的，名为 std::shared_ptr.您的编译器/标准库可能实际上已经支持它们.如果没有，您可以在 boost 的众多优秀库中找到它们.

The current standard only knows one smart pointer, named std::auto_ptr, which would would do what you need in this case. The next standard will come with several more, among them a replacement for std::auto_ptr, named std::unique_ptr, and one with shared ownership semantic, named std::shared_ptr. Your compiler/std lib might actually already support them. If not, you can find them among the many great libraries to be found at boost.

顺便说一句，请注意我已经用 ++i 替换了你的 i++.在 int 的情况下，这不会对您的场景产生任何影响，但是对于某些类型 i++ 可能会创建不必要的副本.(如果你不关心效率，为什么要用 C++ 编程?)

BTW, note that I have replaced your i++ with ++i. In case of an int this doesn't make any difference in your scenario, but there are types for which i++ might create an unnecessary copy. (If efficiency wouldn't concern you, why program in C++?)

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