• Niovol <niovol gmail.com> Apr 21 2007
• Derek Parnell <derek psych.ward> Apr 21 2007

Niovol <niovol gmail.com> writes:

I have written following code:
---------------------------
import std.stdio;
class Abc
{
public:
	int	add(int a, int b) { return a + b; }
}
void main()
{
	Abc abc;
	int a = abc.add(1, 2);
}
----------------------------
Upon compilling and building I executed a program. The message
appeared: "Error: Access Violation". What should I do to use
classes?

Derek Parnell <derek psych.ward> writes:

On Sat, 21 Apr 2007 12:46:14 +0000 (UTC), Niovol wrote:

 I have written following code:
 ---------------------------
 import std.stdio;
 class Abc
 {
 public:
 	int	add(int a, int b) { return a + b; }
 }
 void main()
 {
 	Abc abc;
 	int a = abc.add(1, 2);
 }
 ----------------------------
 Upon compilling and building I executed a program. The message
 appeared: "Error: Access Violation". What should I do to use
 classes?


Firstly, this newsgroup is o longer active. Please use the group
"digitalmars.D" next time.

But back to your problem. Unlike C++, D requires that all classes be
instantiated before use. That means, you must use a 'new' statement on your
object before trying to access it. In D, a simple declaration such as your 

  Abc abc;

only allocates space for a null reference.

This should work ...

 import std.stdio;
 class Abc
 {
 public:
 	int	add(int a, int b) { return a + b; }
 }
 void main()
 {
 	Abc abc = new Abc; // Must be instantiated before use.
 	int a = abc.add(1, 2);

        Abc def;
        int b;
        def = new Abc;  // 'new' before use.
 	b = abc.add(3, 4);

 }


-- 

Derek Parnell
Melbourne, Australia
"Justice for David Hicks!"
skype: derek.j.parnell