super

The super keyword can be used to call a method of the same name in the superclass of the class making the call. Values passed to the super call are passed into the parent method.

Example:

 class SomeClass
   def initialize(name)
   end
 end

 class ChildClass < SomeClass
   def initialize(name, value)
     super(name)
   end
 end

A call to the initialize function of the child class above will result in the execution of both its body and the body of the initialize function in the parent class.

Note that if you invoke super without arguments, all arguments to executing method will be passed to the parent method as well - and if parent's signature does not match the number of arguments, an exception will be raised. So, if the child version of the method uses a different number of arguments than the version in superclass, you need to list arguments that you want to pass to the parent's version of the method.

Note also that you can use any method name, not just initialize (in this case).

iterators

Iterators provide a method for cycling through a set of values and performing an operation, usually specified by a code block, for each value. Iterator functionality is often provided through the mixin Enumeration module.

The first iterator that Ruby programmers are likely to encounter is the each iterator.

Example:

 arr = [1,2,3]
 arr.each do |number|
   put number
 end

Outputs:

 1
 2
 3

yield

yield executes the entire code block passed to the method.

Example:

 def do3times
   yield
   yield
   yield
 end
 
 do3times { puts "yielding..." }

Outputs:

 yielding...
 yielding...
 yielding...

You can therefore make your own method looking like the built-in times:

 class Fixnum
   def times_plus1
     i = 1
     while i <= self + 1
       i += 1
       yield
     end
   end
 end

 5.times_plus1 { puts "yielding..." }

Outputs:

 yielding...
 yielding...
 yielding...
 yielding...
 yielding...
 yielding...