what is a static class

[kumar_mk]

hello toxcct, it was asked to me in an interview, u r saying we have a static class , like static class A{ ----- }; and if i create an object for it what happens??? kk

[kumar_mk]

hello cedric, it was an interview question, u mean to say i can declare a class as static like static class A{----}; what is its purpose, please elaborate on single instance of a class, u mean when i create an object for this class thanks kk

[kumar_mk]

hi alok, no not a singleton class, it was an interview question abt the static class, do we have it just like a static member variable and static function, wat is its significance/purpose?? can i create an object for this static class?? wat happens? thank u, kk

[toxcct]

dude !!! didn't you read what i said, or didn't you understand ? when i say you cannot define a class as static, it means that you CANNOT define a class like you do :

static class CFoo { // No !!! compilation error
// You cannot apply the static keyword to a type definition
//...

};

what i said however is that you are allowed to declare an instance of a class as static, that means a variable which type is a user-defined type :

#include "Foo.h"

static CFoo foo; // Allowed ! foo variable of type CFoo is static

now, what don't you understand ? you'd certainly google the internet or even better, search a good C++ book for static concept...

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TOXCCT >>> GEII power

[VisualCalc 3.0  updated ][Flags Beginner's Guide  new! ]

[Maxwell Chen]

The code snipet below demonstrates the variable instance obj to be static not the type Type, even though it would be confusing you.

#include <iostream>

int main()
{
static class Type
{
public:
void Hello() { std::cout << "Type::Hello() \n"; }
} obj;
obj.Hello();
return 0;
}

Which is equivelent to:

#include <iostream>

int main()
{
class Type
{
public:
void Hello() { std::cout << "Type::Hello() \n"; }
};
static Type obj;
obj.Hello();
return 0;
}

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Maxwell Chen

[toxcct]

i hesitated to show off this example, but finally didn't, thinking it would confuse most beginners around. by the way, it is perfectly legal to do so, as we declare a variable with the type definition inlined...

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TOXCCT >>> GEII power

[VisualCalc 3.0  updated ][Flags Beginner's Guide  new! ]

[Maxwell Chen]

And a further example to demonstrate that the member variables are not shared among individual static instances.

#include <iostream>

static class Type
{
int v;
public:
void Hello() {
std::cout << "Type::Hello() \nv = " << v << " \n";
}
void Hello(int n) {
v = n;
std::cout << "Type::Hello(" << v << ") \n";
}
} g_obj, g_objx;

int main()
{
std::cout << "g_obj \n";
g_obj.Hello(3);
g_obj.Hello();
std::cout << "g_objx \n";
g_objx.Hello();
return 0;
}

The output goes to:

g_obj
Type::Hello(3)
Type::Hello()
v = 3
g_objx
Type::Hello()
v = 0

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Maxwell Chen

[Stephen Hewitt]

C# has the concept of a static class: a static class is a class that contains only static members and instances can't be created with the new keyword. C++ has no such concept; although you can create classes with only static members you do so explictly and the compiler will not stop you from adding a non-static member. Steve

[ThatsAlok]

kumar_windows wrote:

u r saying we have a static class , likestatic class A{ ----- };and if i create an object for it what happens???

Dude There is nothing like Static class, as class doesnot have any address till is object is created, so how can you make anything static which doesn't exist till it object is created

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers, Alok Gupta VC Forum Q&A :- I/ IV

[Nemanja Trifunovic]

kumar_windows wrote:

is there any thing like static class in c++

No.

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