How to initialize private static constant array of the same class C++

August 20, 2023

I need to make class B to work with graph of related objects of class A. An instance of B contains A by value, and links to linked B objects(array indexes). Array of B must to be private as OOP principles dictate. I have long generated initialization list.

//What I want to do(not working)
header:
class A{};

class B{
    static const B array[24]={B(A(),0,0,0,0,0,0),//zeros are numbers
                            ...............//many rows
                            B(A(),0,0,0,0,0,0)};
    A a;
    char l[6];
public:
    B(A _a,char l1, char l2, char l3,char l4, char l5, char l6);
};

//attempt with initialization in cpp
header:
class A{};

class B{
    static const extern B array[24];
    A a;
    char l[6];
public:
    B(A _a,char l1, char l2, char l3,char l4, char l5, char l6);
};

cpp:
static const B::array={B(A(),0,0,0,0,0,0),//zeros are numbers
                       ...............//many rows
                       B(A(),0,0,0,0,0,0)};

I tried above and similar variants. Compiler says I can’t use conflicting specifiers or incomplete types or that field was private. In the past instead of class I used namespace and it worked, but that way array is not encapsulated.

//global variable in namespace(works, but not private)
header:
class A{};

class B{
    A a;
    char l[6];
public:
    B(A _a,char l1, char l2, char l3,char l4, char l5, char l6);
};

namespace B{
const extern B array[24];
}

cpp:
const B array[24]={B(A(),0,0,0,0,0,0),//zeros are numbers
                   ...............//many rows
                   B(A(),0,0,0,0,0,0)};
}

I expect a way to make preinitialized private static array somehow.

>Solution :

Unsure what you tried differently … that seems to compile (and run):

class A{};

class B{
    static const B array[2];
    A a;
    char l[6];
public:
    B(A _a,char l1, char l2, char l3,char l4, char l5, char l6) {}
};

const B B::array[2]={B(A(),0,0,0,0,0,0), B(A(),0,0,0,0,0,0)};

int main() {}