Ruby

Philosophy

• Focus is on the programmer rather than the machine. i.e. maximize programmer efficiency.
• Principle of least astonishment - behave in such a way that minimized the confusion of experienced Ruby programmers.
• Ruby is an object-oriented scripting language.
• Multi paradigm :
  • Scripting : automate tasks within some environment
  • Imperative : traditional control structures
  • Object oriented : everything is an object
  • Functional : Also exists. Computation proceeds via the evaluation of functions that depend only on their input, not program state.

Classes and Inheritance

class MyClass
   @boo #instance variable
   def my_method
     @foo = 2 #instance variable
   end
end

mc = MyClass.new #create a myclass object
mc.my_method     #calls the method
mc.boo           #error, not allowed to access variable

• An instance variable can only be accessed or modified within a method definition.

class MyClass
 def boo  #getter method
   return @boo
 end

 def boo=(val) #setter method
   @boo = val
 end
end

mc = MyClass.new #create a myclass object
boo = 1 #calls the setter method
boo  #calls the getter method

• No return values specified in the method. The value of the last expression executed in the method is its return value.

def min (x,y)
  if x < y then x else y end
end

• When invoking a method, parentheses are optional.
• Class methods (static methods) are created in the same way as normal methods, except are prefixed with keyword "self".
• Array.methods returns all methods in the Array class.
• Ruby convention is to use the last character of a method name to indicate its behaviour. e.g ? is used to indicate return of boolean. "!" is changing the state of the object.
• self refers to the current object. (similar to this)
• Only single inheritance is supported, but mixin capability offers multiple inheritance.
• Classes are NEVER closed, always add more instance vars, methods etc. (Both built in and custom classes)

<syntaxhighlight lang="ruby"> class Fixnum #built in ruby class

def previous #add a new method
  return self -1
end

end <syntaxhighlight>