从C ++中的另一个数组初始化结构内部的数组

问题描述：

struct sample {
    int x;
    int y;
    int arr[10];
};

int arr2[10] = {0, 1, 2, 4, 3, 2, 2, 1, 5, 5};

int a = 19; 
int b = 22;
struct sample* samp = new sample;
samp->x = a;
samp->y = b;
samp->arr = ??

在上面的示例中，我需要使用元素 arr2 [10] 初始化结构 arr [10] 中的数组.

In the above example, I need to initialize array inside the structure arr[10] with the elements of arr2[10].

如何在C ++中实现?

How to do it in C++??

答

如何在C ++中实现?

How to do it in C++??

最简单的解决方案是使用别人所说的std::copy. 不要在C ++中使用memcpy，因为std::copy对于POD一样，但也适用于非POD，并且正确地做事".如果阵列中的类型一天更改一次，则必须重新访问进行此复制的所有位置并替换memcpy. (而且您将错过其中一个地方，并且很难找到该错误).在C ++中使用memcpy没有任何好处，因此从一开始就使用std::copy.

The simplest solution is to use std::copy as was said by others. Do not use memcpy in C++, as std::copy does the same for PODs but also is applicable for non-PODs and just Does The Right Thing. If the type in your array changes one day, you would have to revisit all places where you do such a copy and replace the memcpy. (And you will miss one of the places and have a hard time to find the bug). Using memcpy in C++ has no benefits, so use std::copy from the start.

更好的解决方案是使用C ++数据结构，在这种情况下，请使用std::array

The better solution would be to use C++ data structures, in this case, use std::array

#include <array>
struct sample {
      int x;
      int y;
      std::array<int, 10> arr; //C++ array instead of plain C array
    };

int main()
{
    std::array<int, 10> arr2 = {0, 1, 2, 4, 3, 2, 2, 1, 5, 5};

    int a = 19; 
    int b = 22;

    // 1: no need to say "struct sample*" since C++98
    // 2: prefer to use smart pointers..
    //sample* samp = new sample; 
    std::unique_ptr<sample> samp(new sample());
    samp->x = a;
    samp->y = b;
    samp->arr = arr2; //it's as easy as it should be!

    // 3: ... so ypu can't forget to delete!
    //delete samp;
}

我在这里使用了unique_ptr，尽管在这个小示例中，您根本不需要使用堆分配.还要引入Grijesh的初始化:

I used unique_ptr here, although in this little example you don't need to use heap allocation at all. To bring in Grijesh's initialization in as well:

int main()
{
    std::array<int, 10> arr2 = {0, 1, 2, 4, 3, 2, 2, 1, 5, 5};

    int a = 19; 
    int b = 22;

    sample samp = {a, b, arr2}; //done!
}

无需分配，无需清理，无需按元素分配.

no allocation, no cleanup, no element-wise assignment needed.

从C ++中的另一个数组初始化结构内部的数组

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