How to initialize a const char array data member with C++?

Question

I have a question related to C++ class member initialization. The following code illustrates my question:

class ABCD
{
public:
    ABCD():ObjNum(3){};
    ~ABCD() {};
     static const  unsigned char getByte[8];
     const int ObjNum;


};

const unsigned char ABCD::getByte[8] = {
    'a','b','c','d','e','f','g','h'
};

int main() 
{
     ABCD test;
     cout<<test.getByte[3]<<endl;


     return 0;
}

The above codes work very well, but now if I do not set getByte[8] as static, how could I initialize the class? I have tried in this way, but failed:

class ABCD
{
public:
    ABCD():ObjNum(3),getByte('a','b','c','d','e','f','g','h')
    {

    };
    ~ABCD() {};
    const  unsigned char getByte[8];
     const int ObjNum;


};



int main() 
{
     ABCD test;
     cout<<test.getByte[3]<<endl;


     return 0;
}

The error I have obtained is as follows:

 error C2536: 'ABCD::ABCD::getByte' : cannot specify explicit initializer for arrays

I understand the reason why I got the error, but I do not know how to fix it. Any idea? Thanks!

Do you really need a char array? It is better to use std::string. If you use C++11 you have also std::array that you can initialize with std::initializer_list. — user1434698
– user1434698, Commented Aug 21, 2012 at 8:05
What's wrong with the first code and why do you want to change it? — SingerOfTheFall
– SingerOfTheFall, Commented Aug 21, 2012 at 8:05
@SingerOfTheFall There is nothing wrong with the first code, and it is just out of curious. — feelfree
– feelfree, Commented Aug 21, 2012 at 8:08

betabandido · Accepted Answer · 2012-08-21 08:19:05Z

4

In C++11 you can initialize it like this:

ABCD() : ObjNum(3), getByte{'a','b','c','d','e','f','g','h'} {}

If you are going to use C++11, though, it would be better to use std::array as others have suggested in the comments. You could then define the array like:

const std::array<unsigned char, 8> getByte;

and initialize it in this way (note the double braces):

ABCD() : ObjNum(3), getByte{{'a','b','c','d','e','f','g','h'}} {}

edited Aug 21, 2012 at 8:19

answered Aug 21, 2012 at 8:08

betabandido

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1 Comment

betabandido Over a year ago

@GrzegorzHerman Indeed... the three of us just posted the same solution :)

Grzegorz Herman · Accepted Answer · 2012-08-21 08:08:42Z

3

In C++11 you can initialize arrays like this:

ABCD() : getByte { 'a','b','c','d','e','f','g','h' }
{ ... }

answered Aug 21, 2012 at 8:08

Grzegorz Herman

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Comments

user1434698 · Accepted Answer · 2012-08-21 08:15:14Z

1

It is better to abandon C arrays. In C++ it is better to use std::string. In this case:

class A
{
public:
   A() : s("abcdefgh") {}

private:
   std::string s;
}

In C++11 you can use std::array and use std::initializer_list

class A
public:
   A() : s{'a','b','c','d','e','f','g','h'} {}

private:
   std::array<8> s;
}

answered Aug 21, 2012 at 8:15

user1434698

1 Comment

Craig.Feied Over a year ago

In embedded code the use of std::string comes with many problems.

Alexander Chertov · Accepted Answer · 2012-08-21 08:16:06Z

1

In C++03 you can change the member to be of type boost::array and initialize it in the constructor with a function that returns boost::array<char,8>.

answered Aug 21, 2012 at 8:16

Alexander Chertov

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Comments

Some programmer dude · Accepted Answer · 2012-08-21 08:16:41Z

1

If you have a C++11 compatible compiler, you should be able to use like this:

ABCD():ObjNum(3),getByte{'a','b','c','d','e','f','g','h'}

~~But if your compiler can't handle that you have to initialize the array manually in the constructor, either element by element or by having another array and then do e.g. memcpy.~~

Edit: If your compiler cant handle the C++11 syntax, you're pretty much out of luck. However, GCC since at least version 4.4, and also VC++2010, do handle it. So unless you have requirements forcing you to use "ancient" compilers it shouldn't be a problem.

edited Aug 21, 2012 at 8:16

answered Aug 21, 2012 at 8:08

Some programmer dude

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