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constant trouble.

Posted on 2004-08-04
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Last Modified: 2010-04-01
Hi,
I wish to have an array that will remain constant in my class.

eg.

class A
{
  private:
      const BYTE myData[] = {0x1,0x1,0x1,0x1,0x1};
}


..As you may guess, the compiler throws a syntax error at the '{'.

Whats the best way to achieve this?

TIA

David.
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Question by:dave_p_r_b
  • 3
4 Comments
 
LVL 30

Accepted Solution

by:
Axter earned 125 total points
ID: 11715325
You should make this a static variable.
Example:
class A
{
 private:
      static const BYTE myData[5];
};

//In your cpp file
const BYTE A:myData[5] = {0x1,0x1,0x1,0x1,0x1};

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LVL 30

Expert Comment

by:Axter
ID: 11715371
Correction:
//In your cpp file
const BYTE A::myData[5] = {0x1,0x1,0x1,0x1,0x1};

Since you want this to be a constant variable that is set at compile time, there really is no need for each instance of your object to carry an instance of the constant data.
And in fact it would make your code less efficient if you used a non-static data member.

By making it static, you can then initialize it in your *.cpp file.

continue....
0
 
LVL 30

Expert Comment

by:Axter
ID: 11715437
Alternate method:

class A
{
 private:
     const BYTE* GetMyData()
     {
          const BYTE myData[] = {0x1,0x1,0x1,0x1,0x1};
          return myData;
     }
};

You can use above code as in following:
BYTE xx = GetMyData()[2];
0
 
LVL 39

Expert Comment

by:itsmeandnobodyelse
ID: 11728054
Another method (if you don't need sizeof(myData) in your prog)

class A
{
  private:
      const BYTE* myData ;
  public:
      const BYTE* getMyData()
      {  
            BYTE* pData = new BYTE[5];
            for (int i = 0; i < 5; i++)
                  pData[i] = 0x01;
            return pData;
      }
      A() :  myData(getMyData()) {}      
};

However, if all instances have the same data, Axter's static member is the best solution.

Regards, Alex



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