static data members in a class.....

[epx]

Ok, I have 3 static data members defined for a class "calculator" in a file ('calculator.h') how do initialize these for use?
The three data memberes are:
static float display
static float num1
static char command

i have tried putting them in the constructor like this:

float calculator::display = 0;
float calculator::num1 = 0;
char calculator::command = ' ';

it gives me these errors:

E:\School\CPS271\mp2\calculator.cpp(15) : error C2655: 'display' : definition or redeclaration illegal in current scope
E:\School\CPS271\mp2\calculator.cpp(15) : error C2655: 'num1' : definition or redeclaration illegal in current scope
E:\School\CPS271\mp2\calculator.cpp(15) : error C2655: 'command' : definition or redeclaration illegal in current scope

When I take off scope resolution it gives me these errors:

calculator.obj : error LNK2001: unresolved external symbol "private: static float calculator::display" (?display@calculator@@0MA)
calculator.obj : error LNK2001: unresolved external symbol "private: static float calculator::num1" (?num1@calculator@@0MA)
calculator.obj : error LNK2001: unresolved external symbol "private: static char calculator::command" (?command@calculator@@0DA)

Anyone have a clue??

Thanks again!

 

[Guest_imported]

Static member initialization occurs in class scope. Therefore, they can access other member data or functions.

class SomeClass
{
private:
static int m_someValue;
};

// in your cpp file
int SomeClass::m_someValue = 1;

 

[epx]

I did that...look at the message above. It just doesn't work for some reason.

 

[tchouch]

You must initialize them out of Functions (for example, at begin of calculator.cpp file as follow):
float calculator::display = 0;
float calculator::num1 = 0;
char calculator::command = ' ';

calculator:: calculator()
{
}

 

[tchouch]

It works for another classes so as shown by 'epx' and me.
Without Your code I can ask some Questions only.
May be Your header is included twice? Do You use #ifndef/#endif in *.h - Files to avoid it?
Or have You or Microsoft or another Firm declared class 'calculator' in another Files? Or parent - class have such variables?
And why all Errors are on the Line 15? Are all definitions in the same line?