Method Visibility in Ruby

Method visibility in Ruby refers that instance methods can be public, private or protected. Methods are by default public unless they are explicitly declared private or protected. Method visibility is used in Ruby to achieve Data Abstraction i.e showing only required information and hiding the background details.

Method visibility depends on the three types of access modifiers of a class in Ruby:

Public Access Modifier

Protected Access Modifier

Private Access Modifier

Public Access Modifier

The methods of a class which are public are easily called from any part of the program.
Example :#1

# program to illustrate public access modifier

# defining class
class Geeks

    # methods are public by default
    def publicMethod1
        puts "publicMethod1 called!"
    end

    # using public keyword
    public

    def publicMethod2
        puts "publicMethod2 called!"
    end

end

# creating the object
obj = Geeks.new()

# calling methods
obj.publicMethod1()
obj.publicMethod2()

Output:

publicMethod1 called!
publicMethod2 called!

In the above, program two public methods publicMethod1() and publicMethod2() of the class Geeks are called.

Protected Access Modifier

The methods of a class which are declared protected can only be called from the class in which it is declared and the classes derived from it.
Example :#2

# program to illustrate protected access modifier

# super class
class Parent

    # protected keyword
    protected
  # protected method
  # can not be called directly
  def protectedMethod
        puts "protectedMethod called!"
    end

end

# sub class
class Geeks < Parent

  def publicMethod
    # protected method called in public method
    self.protectedMethod
  end

end

# creating object
obj = Geeks.new

# calling method
obj.publicMethod

Output:

protectedMethod called!

In the above program, the protectedMethod() of Parent class is not accessible directly, so it is called from the publicMethod() of the derived class Geeks.

Private Access Modifier

The methods of a class which are declared private are called within the class only, private access modifier is the most secure access modifier.
Example :#3

# program to illustrate private access modifier

# defining class
class Geeks

    # private keyword
    private
  # private method
  # can not be called directly
  def privateMethod
        puts "privateMethod called!"
  end
  # public keyword
  public
  # public method
  def publicMethod
    # private method called in public method
    privateMethod
  end

end

# creating object
obj = Geeks.new

# calling method
obj.publicMethod

Output:

privateMethod called!

In the above program, the privateMethod() of the Geeks class an not be called directly. So it is called from the publicMethod() of the class Geeks.

Now let us look at another program which demonstrates Method Visibility.
Example :#4

# program to illustrate Method Visibility

# super class
class Parent

  private
  # private method
  def privateMethod
    puts "privateMethod called!"
  end

  protected
  # protected method
  def protectedMethod
        puts "protectedMethod called!"
    end

  public

  # public methods
  def publicMethod1
    puts "publicMethod1 called!"
  end
  def publicMethod2
    # protected method called in public method
    protectedMethod
    # private method called in public method
    privateMethod
  end

end

# sub class
class Child < Parent

  # public method
  def publicMethod3
    # protected method called in public method
    protectedMethod
  end

end

# creating object
obj1 = Parent.new
obj2 = Child.new

# calling method
puts "\nParent methods: \n"
obj1.publicMethod1
obj1.publicMethod2
puts "\nChild methods: \n"
obj2.publicMethod1
obj2.publicMethod3

Output:

Parent methods: 
publicMethod1 called!
protectedMethod called!
privateMethod called!

Child methods: 
publicMethod1 called!
protectedMethod called!