如何从函数返回数组? [英] How to return an array from a function?

问题描述

如何从方法返回一个数组，我必须如何声明它?

How can I return an array from a method, and how must I declare it?

int[] test(void); // ??

推荐答案

int* test();

但是使用向量会是更多的 C++":

but it would be "more C++" to use vectors:

std::vector<国际 >test();

编辑
我会澄清一些观点.既然你提到了 C++，我会用 new[] 和 delete[] 操作符，但它与 malloc/free 相同.

EDIT
I'll clarify some point. Since you mentioned C++, I'll go with new[] and delete[] operators, but it's the same with malloc/free.

在第一种情况下，您将编写如下内容:

In the first case, you'll write something like:

int* test() {
    return new int[size_needed];
}

但这不是一个好主意，因为您的函数的客户端并不真正知道您返回的数组的大小，尽管客户端可以通过调用 delete[] 安全地释放它.

but it's not a nice idea because your function's client doesn't really know the size of the array you are returning, although the client can safely deallocate it with a call to delete[].

int* theArray = test();
for (size_t i; i < ???; ++i) { // I don't know what is the array size!
    // ...
}
delete[] theArray; // ok.

更好的签名是这个:

int* test(size_t& arraySize) {
    array_size = 10;
    return new int[array_size];
}

您的客户端代码现在是:

And your client code would now be:

size_t theSize = 0;
int* theArray = test(theSize);
for (size_t i; i < theSize; ++i) { // now I can safely iterate the array
    // ...
}
delete[] theArray; // still ok.

由于这是 C++，std::vector 是一种广泛使用的解决方案:

Since this is C++, std::vector<T> is a widely-used solution:

std::vector<int> test() {
    std::vector<int> vector(10);
    return vector;
}

现在您不必调用 delete[]，因为它将由对象处理，您可以安全地迭代它:

Now you don't have to call delete[], since it will be handled by the object, and you can safely iterate it with:

std::vector<int> v = test();
std::vector<int>::iterator it = v.begin();
for (; it != v.end(); ++it) {
   // do your things
}

哪个更简单更安全.

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