The best language I have ever learned

Is the best a reachable goal?

Know your limitations. Choose what’s best for the problem.

My problem was the WEB. My solution was RUBY.

@zamith

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WHAT MAKES RUBY GREAT IS that it’s REALLY Object Oriented, dynamically typed, for me and most of all it’s optimized for the programmer’s productivity and happiness!

I wanted a scripting language that was more powerful than Perl, and more object-oriented than Python. “ Yukihiru “Matz” Matsumoto creator of Ruby

GETTING DOWN TO THE BASICS

def hello_world() return "Hello world!" end hello_world() This is a valid method, def hello_world "Hello world!" end hello_world but this is too...

class Lecture def initialize(name = "TBA", duration_in_min = 30) @name = name @duration = duration_in_min/60.0 end def description "Name: #{@name}\nDuration: #{@duration} hours" end end lecture = Lecture.new("Ruby", 45) lecture.description It’s object oriented

// Java maximum = Math.max(1, 3) # Ruby maximum = [1, 3].max # Python positive = abs(num) # Ruby positive = num.abs // C length = strlen(name) # Ruby length = name.length It’s REALLY object oriented

There are ARRAYS arr = [1, “second”, 3.14] There are HASHES hash = {1 => “second”} hash[1] And there are SYMBOLS direction = :north

BLOCKS

sum = 0 (1..5).each do |n| # same as [1,2,3,4,5] sum += n end This is a block... ... used as an iterator.

They are basically closures, that can be stored in variables and called anywhere. They can use variables from the surrounding scope. In Ruby you have blocks, Procs and lambdas which are all similar.

ITERATORS

In Ruby the iterator is internal to the collection, unlike Java. It’s just a method that calls yield every time it generates a new value. Ruby already provides a lot of useful iterators: each, map, inject, etc...

def fib(max) i1, i2 = 1, 1 # parallel assignment while i1 <= max yield i1 i1, i2 = i2, i1+i2 end end fib(1337) { |n| print n } You can build your own:

SHARING FUNCTIONALITY

class SuperClass def hello_world "Hello world!" end end class SubClass < SuperClass end superclass = SuperClass.new subclass = SubClass.new Single inheritance Built-in functionality comes from the Object class

module ToBeIncluded def foo "bar" end end class MyClass include ToBeIncluded end Mixins are modules that are included... ...into classes or other modules

When to use them? You should evaluate the relation between the objects. a is a b, use inheritance a has a b, use composition a behaves like b, use mixins

REFLECTION

Reflection is the ability to examine an object at runtime.

You can transverse all living objects ObjectSpace.each_object { |x| puts x } You can look inside objects [1,2,3].methods [1,2,3].respond_to?(:to_s) [1,2,3].kind_of?(Hash) You can invoke methods without knowing their names a = [1,2,3] a.send(a.private_methods.first.to_sym) You can know about the runtime environment Fixnum.class_variables print File.read(__FILE__)

METAPROGRAMMING

The writing of programs that write or manipulate other programs (or themselves).

Ruby allows you to define methods at runtime class BabyInfo ["cry", "eat"].each do |baby_action| define_method(baby_action) do "Of course, babies #{baby_action}" end end end

There are some callbacks you can use class BabyInfo ["cry", "eat"].each do |baby_action| define_method(baby_action) do "Of course, babies #{baby_action}" end end def method_missing(name, *args, &blk) "Nope, babies don’t #{name}" end end

There are many others, such as method_added, included, inherited... Metaprogramming in Ruby is a very powerful tool and therefore must be used with care. You can even modify String, Float or even Class and Object

LEARN RUBY

THANKS and special thanks to Gonçalo Silva

@ZAMITH blog.zamith.pt