Declaring a non static const array as class member

Question

How can we declare a non static const array as an attribute to class. Following code produces compilation error (“'Test::x' : member could not be initialized”)?

class Test
{
public:
 const int x[10];

public:
 Test()
 {
 }
};

Answer 1

You should read this already posted question. Since it is not possible to do what you want, the workaround is to use an std::vector.

Answer 2

You could use array class from tr1.

class Test
{
public:
 const array<int, 10> x;

public:
 Test(array<int,10> val) : x(val) // the only place to initialize x since it is const
 {
 }
};

array class could be simplistically represented as follows:

template<typename T, int S>
class array
{
    T ar[S];
public:
    // constructors and operators
};

Answer 3

Using boost::array (the same as tr1) it will looks like:

    #include<boost/array.hpp>

    class Test
    {   
       public:

        Test():constArray(staticConst) {}; 
        Test( boost::array<int,4> const& copyThisArray):constArray(copyThisArray) {}; 

        static const boost::array<int,4> staticConst; 

        const boost::array<int,4> constArray;
    };

    const boost::array<int,4> Test::staticConst = { { 1, 2, 3 ,5 } };

The extra code static member is needed because { { 1, 2, 3 ,5 } } is invalid in initialization list.

Some advantages is that boost::array have defined iterator and standard container methods like size, begin and end.