Ruby Documentation

Introduction

Ruby is a programming language with the following properties:

Dynamic - Programming behaviours are executed at runtime

Interpreted - Most instructions executed directly without first compiling them into machine code

Reflective - Capable of modifying its strcture and behaviour at runtime

Object-oriented - Objects containing data and methods instantiated from classes to enable a modularized code base

General purpure - Used in a wide variaty of domains.

It was created in 1995 by Yukihiro Matsumoto.

Hello World

To print out "Hello World" the console:

puts "Hello World"

'Puts'is short for put string. It ends with a newline (\n) returns undefined.

Variables

Variables are declared without needing to explicitly define the type. It is clear to ruby what type the variable is from how you declare it

a = "I am a string" 
b = 3 #Fixnum
c= 3.3 #Float

Everything in ruby is an object - which means that each time you declare a variable as in the case above, these variables have access to a wide variaty of methods inherant in the type of object that is instantiated as.

Variable scope

There are four levels of variable scope:

g = "I am a global variable" #defined outside of any Function
def someFunction
    l =  "I am a local variable" #can only be accessed from within the function
end

def class MyClass
    @@class_var = "I am a class variable" #Available to any instantiation of the class
    def classFunction
        @instance_var = "I am an instance variable" #Available to every function within an instance of the class
    end
end

Constants

A Ruby constant is like a variable, except that its value is supposed to remain constant for the duration of the program. The Ruby interpreter does not actually enforce the constancy of constants, but it does issue a warning if a program changes the value of a constant.

A_CONSTANT = "I am a constant"

Ruby knows that you have declared a constant from the all caps declaration.

Data types

These are the basic data types in ruby:

s = "I am a string"
fixnum = 3 #number Fixnum (integer)
float = 3.3 #number Float
array = ["a", 1, 2, "hello"] #Array
hash = {name: "Robin", lastName: "Bson"} #Hash
s = :unique #Symbol
I_Am_True = true #bolean

Then there are blocks which as far as I know is unique to ruby:

{puts "Hello yo"}
#or
do
    puts "Hello yo"
end
# Pass block to function without having to define it as a function parameter (called when yielded)
def f
    yield
end
f {puts "I am a block"} # => I am a block

Conditionals

If statements:

if x > 2
    puts "x is greater than 2"
elsif x < 2
    puts "x is less than 2"
else
    puts "x is 2"
end

While loop:

while true
    puts "Infinite loop"
end

For-loop

for i in (1..5)
    puts i
    i += 1;
end
#same result
(1..5).each {|i| puts i}

Function declarations

Declaring and using a function is simple enough:

def quad(x)
    x**4
end
quad(4) # => 256

Notice abscence of return-keyword. A ruby function/method returns the last line of the function by default

Reference

This site has been made to practice writing technical doucumentation pages. For a complete guide on the ruby languate i recommend Ruby-doc.org.