Member variable

In object-oriented programming, a member variable (sometimes called a member field) is a variable that is associated with a specific object, and accessible for all its methods (member functions). In class-based languages, these are distinguished into two types: if there is only one copy of the variable shared with all instances of the class, it is called a class variable or static member variable; while if each instance of the class has its own copy of the variable, the variable is called an instance variable.

Examples

C++

class Foo {
    int bar; // Member variable
  public:
    void setBar(const int newBar) { 
      bar = newBar;
    }
};

int main () {
  Foo rect; // Local variable

  return 0;
}

Java

public class Program
{
    public static void main(String[] args)
    {
    	// This is a local variable. Its lifespan
    	// is determined by lexical scope.
    	Foo foo;
    }
}

public class Foo
{
    /* This is a member variable - a new instance
     of this variable will be created for each 
     new instance of Foo.  The lifespan of this
     variable is equal to the lifespan of "this"
    */ instance of Foo

    int bar;
}

Python

class Foo:

  @property
  def bar(self):
    return self._bar

  @bar.setter
  def bar(self, new_bar):
    self._bar = new_bar


f = Foo()
f.bar = 100
print(f.bar)

See also

• Global variable
• Local variable