step-by-step on basics Ruby

Reference

• 1995, Yukihiro “Matz” Matsumoto
• ruby-lang (pt-Br)
• Code Style

Main characteristics

• Interpreted
• Object Oriented (everithung is object)
• Dynamic and Implicit Types
• Simple, yet robust
• Open Source

Coding

I/O

• puts

puts "Hello World"

• gets

variable = gets

or

variable = gets.chomp

Variables

#Using variables
var_string = "this is a string"
var_integer = 1
var_float = 1.4
var_boolean = true

• Primitives types:
  • String: "whatever"
  • Integer: 1
  • Float: 1.43
  • Boolean: true or false
• Casting/Conversion
  • String: .to_s
  • Integer: .to_i
  • Float: .to_f
• Type checking
  • .class
  • .instace_of?(Type)
• Scope
  • Local
  • Instance (@variable)
  • Constant (Variable or VARIABLE)
  • Global ($variable)

Operators

More in

Assignment

# assignment =
var = 5

Arithmetic

# addition or concatenation +
1 + 2
"asd" + "fgh"

# subtraction -
1 - 2

# multiplication *
1 * 2

# division /
1 / 2

# exponentiation **
2 ** 3

# modulo (remainder) %
3 % 2

Logic

# equals ==
a == b

# not equals !=
a != b

# not
!a

# greater than >
a > b

# greater than or equal to
a >= b

# less than >
a < b

# less than or equal to
a <= b

# boolean And &&
a && b

# boolean OR ||
a || b

String

• Common Methods
  • .size
  • .empty?
  • #{expression} interpolation
  • variable[0,3]: Substring. Starts 0 Size 3
  • .include?(string): returns true if variable contains string

Arrays

arr = [1,2,3,4]
arr = ["1","2","3","4"]
arr = ["1",2,["3"],true]
arr[0] = 10
arr[1] = "some random string"

Conditionals

if v1 > 10
  puts "Greater than 10"
else

or

# using 'then'
if v1 > 10 then
  puts "Greater than 10"
else

# elseif statement
if v1 > 10
  puts "Greater than 10"
elsif v1 > 6
  puts "Greater than 6"
else
  puts "Less than or equal to 6"
end

# using 'unless' conditional
unless conditional
  # if conditional is false
end

# using 'unless' with 'else' statement conditional
unless conditional
  # if conditional is false
else
  # if conditional is true 
end

# ternary operator
conditional ? <success statements> : <failure statements>

Looping

For loop

# using for loop  
for i in arr do
 puts i
end

# using while loop: while conditional is true
while conditional 
  puts "Lucas - #{count}"
  count+=1
end

Until loop

# until loop: while conditional is false
until conditional
 # code to be executed
end

#each loop: for each |element| in arr (array) with an iteration variable
arr.each do |element|
  puts element
end

Each loop

#each loop: for each |element| in range with an iteration variable
(1..5).each do |element|
  puts element
end
#if the range was 1...5, last element would not be considered

or

# each loop: repeats statements the size of the range
(1..5).each do
  #statements
end

Times loop

# times-loop.
5.times do
    puts "a"
end

or

# times-loop with an iteration variable
# starts in 0
5.times do |i|
    puts i
end

Methods & Functions

# using parenthesis
def method_name(parameter_1, parameter_2, ...)
  return x
end

# no parenthesis
def method_name parameter_1, parameter_2, ...
  return x
end

# no 'return' statement
def method_name parameter_1, parameter_2, ...
  x
end