Calling method in parent class from subclass methods in Ruby

Question

I've used super to initialize parent class but I cannot see any way of calling parent class from subclass methods.

I know PHP and other languages do have this feature but cannot find a good way to do this in Ruby.

What would one do in this situation?

Answer 1

If the method is the same name, i.e. you're overriding a method you can simply use super. Otherwise you can use an alias_method or a binding.

class Parent
  def method
  end
end

class Child < Parent
  alias_method :parent_method, :method
  def method
    super
  end

  def other_method
    parent_method
    #OR
    Parent.instance_method(:method).bind(self).call
  end
end

Answer 2

The super keyword calls a method of the same name in the super class:

class Foo
  def foo
    "#{self.class}#foo"
  end
end

class Bar < Foo
  def foo
    "Super says: #{super}"
  end
end

Foo.new.foo # => "Foo#foo"
Bar.new.foo # => "Super says: Bar#foo"

Answer 3

Others have said it already well. Just one additional note of caution:

The syntax super.foo to call method foo in the super class is not supported. Rather it will call the super-method and on the returned result, try to call foo.

  class A
    def a
      "A::a"
    end
  end

  class B < A
    def a
      "B::a is calling #{super.a}" # -> undefined method `a` for StringClass 
    end
  end

Answer 4

The super keyword in Ruby actually calls a method of the same name in the parent class. (source)

class Foo
  def foo
    # Do something
  end
end

class Bar < Foo
  def foo
    super # Calls foo() method in parent class
  end
end

Answer 5

As of Ruby 2.2, super_method can also be used to call super of method a from method b.

method(:a).super_method.call

Answer 6

class Parent
  def self.parent_method
    "#{self} called parent method"
  end

  def parent_method
    "#{self} called parent method"
  end
end

class Child < Parent

  def parent_method
    # call parent_method as
    Parent.parent_method                # self.parent_method gets invoked
    # call parent_method as
    self.class.superclass.parent_method # self.parent_method gets invoked
    super                               # parent_method gets invoked 
    "#{self} called parent method"      # returns "#<Child:0x00556c435773f8> called parent method"
  end

end

Child.new.parent_method  #This will produce following output
Parent called parent method
Parent called parent method
#<Child:0x00556c435773f8> called parent method
#=> "#<Child:0x00556c435773f8> called parent method"

self.class.superclass == Parent #=> true

Parent.parent_method and self.class.superclass will call self.parent_method(class method) of Parent while super calls the parent_method(instance method) of Parent.