Quick reference for getting started with Ruby. Useful for people doing katas, etc. with some programming knowledge but no Ruby experience.

ruby_quick_intro.rb

# These are some useful tips for programming in Ruby
# (Things in ALL_CAPS will be written by you)

# Comments begin with a "#" like this

# A test method
def test_SOMETHING
  assert_equal EXPECTED_VALUE, ACTUAL_VALUE
end

# Functions
def FUNCTION_NAME(PARAMETER_NAME)
    # ...
    return RETURN_VALUE
end

# Example function for square of a number
def square(number)
    return number * number
end
# square(4) => 16
# square(5) => 25
# square(7) => 49


# If/else
if CONDITION
    # do something when CONDITION is true
elsif OTHER_CONDITION
    # otherwise do something when OTHER_CONDITION is true
elsif THIRD_CONDITION
    # otherwise do something with THIRD_CONDITION is true
else
    # do something else
end

# Math
x = 7
y = 91

y / x       # => 13
y % 13      # => 0  (modulo/remainder)
x % 3       # => 1
z = y / x   # => z is 13

# Logic
x = 7

x < 10      # => true
x < 5       # => false
x > 1       # => true
x > 19      # => false
x - 1 == 6  # => true
x % 5 == 0  # => false

# Strings
given_name = "Barak"
surname = "Obama"
full_name = given_name + surname    # => "BarakObama"