We all know that identifiers (variables, objects, functions etc.) may have
two scopes in C++. They may be declared as global or local to a block.
We have seen identifiers like variables and functions to be defined locally
and globally quite often but there is one identifier which is not that commonly
declared as local, yeah you guessed right, its classes.
You might have noticed the fact that classes are almost always declared as
global even when they are to be used only in one block. It is so because of
some reasons that we’ll discuss later.
First let’s have a look at a class declared locally:
// this code contains a local class
#include <iostream.h>
void func();
void main()
{
// myclass unknown here
}
void func()
{
class myclass
{
...
...
};
}
While classes may also be defined as local, there are some restrictions of
what can be done and what cannot be, they are listed below:
Member functions must be inline
Members of local class cannot access other variables within the block
It cannot have static member variables
Here is an example program:
// this code contains a local class
#include <iostream.h>
void func();
void main()
{
// myclass unknown here
func();
}
void func()
{
int num;
class myclass
{
int a;
public:
// member functions MUST be defined
// inside the class
void set(int x)
{
// can't access num
a=x;
}
void show()
{
cout<<a<<endl;
}
};
myclass ob;
ob.set(10);
ob.show();
}
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