栈和堆创建对象数组 [英] Creating array of objects on the stack and heap

问题描述

考虑以下code：

class myarray
{
    int i;

    public:
            myarray(int a) : i(a){ }

}

您如何创建的myArray的对象的堆栈上的数组以及如何创建对象的堆数组？

How can you create an array of objects of myarray on the stack and how can you create an array of objects on the heap?

推荐答案

您可以创建对象对数组堆栈^†通过

You can create an array of objects on the stack^† via:

myarray stackArray[100]; // 100 objects

和堆^†（或的FreeStore）：

And on the heap^† (or "freestore"):

myarray* heapArray = new myarray[100];
delete [] heapArray; // when you're done

但最好自己不要管理内存。相反，使用的std ::矢量：

#include <vector>
std::vector<myarray> bestArray(100);

一个向量是一个动态数组，（默认）从堆中分配的元素。^††

A vector is a dynamic array, which (by default) allocates elements from the heap.^††

由于您的类没有默认构造函数，在堆栈上创建它，你需要让编译器知道该怎么传递到构造函数：

Because your class has no default constructor, to create it on the stack you need to let the compiler know what to pass into the constructor:

myarray stackArray[3] = { 1, 2, 3 };

或者用向量：

// C++11:
std::vector<myarray> bestArray{ 1, 2, 3 };

// C++03:
std::vector<myarray> bestArray;
bestArray.push_back(myarray(1));
bestArray.push_back(myarray(2));
bestArray.push_back(myarray(3));

当然，你总是可以给它一个默认的构造函数：

Of course, you could always give it a default constructor:

class myarray
{
    int i;    
public:
    myarray(int a = 0) :
    i(a)
    {}
};

---

†对于学究：C ++并没有真正有一个堆或堆/的FreeStore。我们所拥有的是自动存储和动态存储的持续时间。在实践中，这赞同堆栈分配和堆分配。

---

† For the pedants: C++ doesn't really have a "stack" or "heap"/"freestore". What we have is "automatic storage" and "dynamic storage" duration. In practice, this aligns itself with stack allocation and heap allocation.

††如果你想从堆栈动态分配，你需要定义一个最大尺寸（堆栈存储事先已知的），然后给矢量新分配器所以它使用堆栈来代替。

†† If you want "dynamic" allocation from the stack, you'd need to define a max size (stack storage is known ahead of time), and then give vector a new allocator so it uses the stack instead.

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