Last Updated : 23 Jul, 2025
A class declared inside a function becomes local to that function and is called Local Class in C++.
For example, in the following program, Test is a local class in fun().
CPP
// C++ program without any compilation error
// to demonstrate a Local Class
#include <iostream>
using namespace std;
// Creating the class
void fun()
{
// local to fun
class Test {
// members of Test class
};
}
// Driver Code
int main() { return 0; }
Following are some interesting facts about Local Classes in C++:
1) A local class type name can only be used in the enclosing function.
For example, in the following program, declarations of t and tp are valid in fun(), but invalid in main().
CPP
// A program without any compilation error to demonstrate
// that a local class type name can only be used
// in the enclosing function
#include <iostream>
using namespace std;
void fun()
{
// Local class
class Test {
// Body
};
Test t; // Fine
Test* tp; // Fine
}
int main()
{
Test t; // Error
Test* tp; // Error
return 0;
}
2) All the methods of Local classes must be defined inside the class only. For example, program 1 works fine and program 2 fails in the compilation.Program 1:
// C++ program without any compilation error to demonstrate
// that all the methods of Local classes must be defined
// inside the class only
#include <iostream>
using namespace std;
void fun()
{
class Test // local to fun
{
public:
// Fine as the method is defined
// inside the local class
void method()
{
cout << "Local Class method() called";
}
};
Test t;
t.method();
}
int main()
{
fun();
return 0;
}
Local Class method() called
Program 2:
CPP
// C++ program with compilation error to demonstrate that
// all the methods of Local classes must be defined inside
// the class only
#include <iostream>
using namespace std;
void fun()
{
class Test // local to fun
{
public:
void method();
};
// Error as the method is defined outside the local
// class
void Test::method() { cout << "Local Class method()"; }
}
int main() { return 0; }
Output
Compiler Error:
In function 'void fun()':
error: a function-definition is not allowed here before '{' token
3) A Local class cannot contain static data members. It may contain static functions though. For example, program 1 fails in compilation, but program 2 works fine.
Program 1:
CPP
// A program with compilation error to demonstrate that
// a Local class cannot contain static data members
#include <iostream>
using namespace std;
void fun()
{
class Test // local to fun
{
static int i;
};
}
int main() { return 0; }
Output
Compiler Error: In function 'void fun()': error: local class 'class fun()::Test' shall not have static data member 'int fun()::Test::i'
Program 2:
CPP
// C++ program without any compilation error to demonstrate
// that a Local class cannot contain static data members
#include <iostream>
using namespace std;
void fun()
{
class Test // local to fun
{
public:
static void method()
{
cout << "Local Class method() called";
}
};
Test::method();
}
int main()
{
fun();
return 0;
}
Local Class method() called
4) Member methods of the local class can only access static and enum variables of the enclosing function. Non-static variables of the enclosing function are not accessible inside local classes. For example, program 1 compiles and runs fine. But, program 2 fails in the compilation.Program 1:
// C++ program without any compilation error to demonstrate
// that member methods of local class can only access static
// and enum variables of the enclosing function
#include <iostream>
using namespace std;
void fun()
{
static int x;
enum { i = 1, j = 2 };
// Local class
class Test {
public:
void method()
{
cout << "x = " << x
<< endl; // fine as x is static
cout << "i = " << i
<< endl; // fine as i is enum
}
};
Test t;
t.method();
}
int main()
{
fun();
return 0;
}
Program 2:
CPP
// C++ program with compilation error to demonstrate that
// member methods of local class can only access static
// and enum variables of the enclosing function
#include <iostream>
using namespace std;
void fun()
{
int x;
// Local class
class Test {
public:
void method() { cout << "x = " << x << endl; }
};
Test t;
t.method();
}
int main()
{
fun();
return 0;
}
Error:
prog.cpp: In member function ‘void fun()::Test::method()’:
prog.cpp:14:43: error: use of local variable with automatic storage from containing function
void method() { cout << "x = " << x << endl; }
^
prog.cpp:9:9: note: ‘int x’ declared here
int x;
^
5) Local classes can access global types, variables, and functions. Also, local classes can access other local classes of the same function. For example, the following program works fine.
// C++ program without any compilation error to demonstrate
// that Local classes can access global types, variables and
// functions
#include <iostream>
using namespace std;
int x;
void fun()
{
// First Local class
class Test1 {
public:
Test1() { cout << "Test1::Test1()" << endl; }
};
// Second Local class
class Test2 {
// Fine: A local class can use other local classes
// of same function
Test1 t1;
public:
void method()
{
// Fine: Local class member methods can access
// global variables.
cout << "x = " << x << endl;
}
};
Test2 t;
t.method();
}
int main()
{
fun();
return 0;
}
Test1::Test1() x = 0
Must Read: Nested Classes in C++
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