CODEWITHSUNDEEP
c++
tdao
tdao

Reputation: 17668

Declare a class member array of structs (C++98)

I need to declare a class member array of structs that is ideally initialized at declaration like this:

class Foo
{
    typedef struct _TMember
    {
        uint16 m_key;
        uint16 m_val;
    }
    TMember;

    TMember m_member_tab[] =
    {
        { 10,    2400},
        { 20,    2500},
        { 30,    2600},
        { 40,    2700},
        { 50,    2650},
    };

    // etc...
};

Can this be done in traditional C++ (pre C++11) class header?

Edit: If not, what would be a good alternative? It'd be good to have the array as a class member, but otherwise it can be defined in a common header file.

Upvotes: 3

Views: 2422

Answers (1)

Petr Skocik
Petr Skocik

Reputation: 60067

Static class variables used to have to be initialized in the implementation file, outside of the header.

With C++11, in-class initialization works if the static class variables is constexpr:

#include <iostream>

class Foo{
  public:
  struct TMember //can't start with an underscore; typedef unecessary in C++
  {
    unsigned short m_key;
    unsigned short m_val;
  };
  constexpr static TMember m_member_tab[]={
    { 10,    2400},
    { 20,    2500},
    { 30,    2600},
    { 40,    2700},
    { 50,    2650},
  };
};
int main()
{
  using namespace std;
  cout<<Foo::m_member_tab[1].m_val<<endl;
}

Old C++:

#include <iostream>

class Foo{
  public:
  struct TMember //can't start with underscore; typedef unecessary in C++
  {
    unsigned short m_key;
    unsigned short m_val;
  };
  static TMember m_member_tab[5];
};
//End of header, start of implementation 

Foo::TMember Foo::m_member_tab[] = {
    { 10,    2400},
    { 20,    2500},
    { 30,    2600},
    { 40,    2700},
    { 50,    2650},
  };
int main()
{
  using namespace std;
  cout<<Foo::m_member_tab[1].m_val<<endl;
}

Upvotes: 5

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