何时在C ++中使用新的？ [英] when to use new in C++?

问题描述

什么是一个好的政策，什么时候使用新来创建类的实例？我一直爱好编程C ++一段时间，但我仍然不确定什么时候是最好的时间做这个：

What's a good policy for when to use "new" to make an instance of a class? I've been hobby programming C++ for a while but I'm still not for sure when is the best time to do this:

MyClass thing(param1, param2);

：

MyClass* thing;
thing = new MyClass(param1, param2);

任何建议？

推荐答案

 MyClass thing(param1, param2); //memory for thing is allocated on the process stack(static allocation)

 MyClass* thing;
 thing = new MyClass(param1, param2); //memory is allocated dynamically on the heap(free store) for thing

这里的区别在于： / p>

The difference lies here:

 int main()
 { 
   {
    MyClass thing(param1, param2); //thing is local to the scope
   } //destructor called for thing
   //cannot access thing (thing doesn't exist)
 } 

 int main()
 {
   {
     MyClass* thing;
     thing = new MyClass(param1, param2);
   }
  //the object pointed to by thing still exists
   //Memory leak
 }  

对于大型对象，您必须动态分配内存（使用new），因为进程堆栈的大小有限。

For large objects you must allocate memory dynamically(use new) because the process stack has a limited size.

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