CODEWITHSUNDEEP
c++
ACK_stoverflow
ACK_stoverflow

Reputation: 3305

How to declare and initialize a static const array as a class member?

Pretty self-explanatory. The array is of an integral type, the contents are known and unchanging, and C++0x isn't allowed. It also needs to be declared as a pointer. I just can't seem to find a syntax that works.

The declaration in Class.hpp:

static const unsigned char* Msg;

Stuff in Class.cpp is really what I've tinkered with:

const unsigned char Class::Msg[2] = {0x00, 0x01}; // (type mismatch)
const unsigned char* Class::Msg = new unsigned char[]{0x00, 0x01}; // (no C++0x)

...etc. I've also tried initializing inside the constructor, which of course doesn't work because it's a constant. Is what I'm asking for impossible?

Upvotes: 32

Views: 137441

Answers (2)

David Rodríguez - dribeas
David Rodríguez - dribeas

Reputation: 208456

You are mixing pointers and arrays. If what you want is an array, then use an array:

struct test {
   static int data[10];        // array, not pointer!
};
int test::data[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

If on the other hand you want a pointer, the simplest solution is to write a helper function in the translation unit that defines the member:

struct test {
   static int *data;
};
// cpp
static int* generate_data() {            // static here is "internal linkage"
   int * p = new int[10];
   for ( int i = 0; i < 10; ++i ) p[i] = 10*i;
   return p;
}
int *test::data = generate_data();

Upvotes: 33

Michael Burr
Michael Burr

Reputation: 340496

// in foo.h
class Foo {
    static const unsigned char* Msg;
};

// in foo.cpp
static const unsigned char Foo_Msg_data[] = {0x00,0x01};
const unsigned char* Foo::Msg = Foo_Msg_data;

Upvotes: 51

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