How to instantiate class within a class?
Say I have a class ClassMain, and ClassMain needs to have a pointer to a ClassA. If I do the following:
ClassMain.h
Is that a problem?
And while I'm at it I might as well ask how this would be done using an initialization list. Or is there an even better way of doing this?
ClassMain.h
#pragma once
#include "ClassA.h"
class ClassMain
{
public:
ClassMain(void);
ClassA *aPtr;
};#include "StdAfx.h"
#include "ClassMain.h"
ClassMain::ClassMain(void)
{
ClassA a;
aPtr = &a;
}Is that a problem?
And while I'm at it I might as well ask how this would be done using an initialization list. Or is there an even better way of doing this?
(This will be an unmanaged code project. I like defining ClassA a at compile time rather than using a new statement.)
SOLUTION
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ASKER
If I instantiate ClassA in my ClassMain.h file, is there a problem with everyone who does #include "ClassMain.h" at the top of their file ends up instantiating another instance of ClassA, a side effect they don't necessarily want?
#pragma once
#include "ClassA.h"
class ClassMain
{
public:
ClassMain(void);
ClassA a;
};SOLUTION
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ASKER
I'm starting to get it. Just including ClassMain.h doesn't instantiate an an instance of that class, it just gives information about the class in case anyone's interested. Creating the instance of ClassMain gives me variable a which is an instance of ClassA, and I don't have to do anything in the constructor of ClassMain to create an instance of ClassA
In C# this wouldn't work because a is never created.:
In C# this wouldn't work because a is never created.:
class ClassMain
{
ClassA a;
public void Run()
{
a.Test();
}
}class ClassMain
{
public:
ClassA a;
void Run()
{
a.Test();
}
};
ASKER
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go in the ClassMain.h file?I thought of putting it there, but then wondered if that meant every one who did #include ClassMain.h would be instantiating an instance of ClassA?