C++ 在初始化列表中初始化一个常量大小的数组
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Initialize a constant sized array in an initializer list
提问by Serge
I've got a situation which can be summarized in the following:
我有一个情况，可以总结如下：
class Test
{
Test();
int MySet[10];
};
is it possible to initialize MySetin an initializer list?
是否可以MySet在初始化列表中进行初始化？
Like this kind of initializer list:
像这种初始化列表：
Test::Test() : MySet({1, 2, 3, 4, 5, 6, 7, 8, 9, 10}) {}
Is there any way to initialize a constant-sized member array in a class's initalizer list?
有没有办法在类的初始化器列表中初始化一个常量大小的成员数组？
回答by oldrinb
While not available in C++03, C++11 introduces extended initializer lists. You can indeed do it if using a compiler compliant with the C++11 standard.
虽然在 C++03 中不可用，但 C++11 引入了扩展初始化列表。如果使用符合 C++11 标准的编译器，您确实可以做到。
struct Test {
Test() : set { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 } { };
int set[10];
};
The above code compiles fine using g++ -std=c++0x -c test.cc.
上面的代码使用g++ -std=c++0x -c test.cc.
As pointed out below me by a helpful user in the comments, this code does not compileusing Microsoft's VC++ compiler, cl. Perhaps someone can tell me if the equivalent using std::arraywill?
正如一位乐于助人的用户在评论中指出的那样，此代码未使用 Microsoft 的 VC++ 编译器 cl 进行编译。也许有人可以告诉我是否等效使用std::array？
#include <array>
struct Test {
Test() : set { { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 } } { };
std::array<int, 10> set;
};
This also compiles fine using g++ -std=c++0x -c test.cc.
这也可以使用g++ -std=c++0x -c test.cc.
回答by John Humphreys - w00te
Unfortunately, in C++03, you cannot initialize arrays in initializer lists. You can in C++11 though if your compiler is newer :)
不幸的是，在 C++03 中，您不能在初始化列表中初始化数组。如果您的编译器更新，您可以在 C++11 中使用 :)
see: How do I initialize a member array with an initializer_list?
回答by Cheers and hth. - Alf
"I understand that Set is just a pointer to the static array of 10 integers"
“我知道 Set 只是一个指向 10 个整数的静态数组的指针”
No, that's wrong: it's an array, not a pointer.
不，这是错误的：它是一个数组，而不是一个指针。
You can still initialize it in the constructor's initializer list.
您仍然可以在构造函数的初始化列表中对其进行初始化。
For a compiler that doesn't support C++11 curly braces initialization (Visual C++ version 11 and earlier comes to mind) you'll have to jump through some hoops though, as shown below:
对于不支持 C++11 花括号初始化的编译器（想到 Visual C++ 版本 11 及更早版本），您将不得不跳过一些障碍，如下所示：
#include <iostream>
#include <vector>
using namespace std;
#define CPP11
#if defined( _MSC_VER )
# if (_MSC_VER <= 1700)
# undef CPP11
# endif
#endif
#ifdef CPP11
class Cpp11
{
private:
int set_[10];
public:
Cpp11()
: set_{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }
{}
int foo() const { return set_[3]; }
};
#endif
class Cpp03
{
private:
struct IntArray10 { int values[10]; };
IntArray10 set_;
static IntArray10 const& oneToTen()
{
static IntArray10 const values =
{ {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} };
return values;
}
public:
Cpp03()
: set_( oneToTen() )
{}
int foo() const { return set_.values[3]; }
};
int main()
{}
Instead of using raw arrays, though, use std::vectorand C+++11 std::array, both of which are supported even by Visual C++ 11.
但是，不要使用原始数组，而是使用std::vector和 C+++11 std::array，即使 Visual C++ 11 也支持这两者。
