All the examples from our introduction to Ruby

ruby-intro.rb

def vader(evil = false)
  #  guard clause
  return "something else" if evil == "luke"

  #  implicit return, last line executed
  if evil
    "i am your father and I hate you"
  else
    "i am your father and i love you"
  end
end

puts "Luke, #{vader(true)}"

puts vader
puts vader("luke")

# eveything is an object
puts"string".class
puts 12345.class
puts 1.423423.class
puts false.class
puts true.class
puts nil.class

# what is the difference between false and nil
def empty_method
  # this will just return nil
end

def false_method
  # this will return false
  false
end

if false
  puts "this will never print"
end

if nil
  puts "this will never print"
end

if "will return true"
  puts "true"
end

if 0
  puts "this will return true"
end

true_value = "string"

if true_value == true
  puts "this wont print"
end

nil_value = nil

if nil_value.nil?
  puts "this is nil"
end

# everything will pass an if condition
# except for false and nil
# this means "check this isn't false or nil"
if true_value
  puts "this will print"
end

def something_true
  true
end

def something_false
  false
end

# and or should always be like this
if something_true && something_false
  puts "wont print"
end

if something_false || something_true
  puts "will print"
end

# strings
# these are two seperate objects
# we can change them and do what we like to them
string = "London"
another_string = "London"

# symbol
#  immutable
#  these are the same
#  use a symbol as a placeholder
# :london
# :london

hash = { :london => "rainy", "London" => "still rainy"}


hash[:london]
# Bad idea if we change the string the hash gets messed up
hash["London"]

# belongs_to :users

# hashes and arrays

arr = [2,3,4,5,5,6,4]
arr << 10
puts arr.inspect

puts arr[0]
puts arr[0..2].inspect

# concatenation
arr = [1,2]
arr = arr + [3,4]
arr += [5,6]
puts arr.inspect

string += " is very rainy"
puts string

#  loops
#
#  don't do this way
for val in arr
  puts val
end

# do it this way
# multi line block
arr.each do |v|
  puts v
end

# one line block
arr.each { |v| puts v }

# there's other loops but we don't often use them
num = 0
while num < 5
  puts "not infinity"
  num += 1
end

num = -0

while true
  puts "looping"
  num +=1
  break if num > 5
end

until num > 5
  puts "nor infinity"
  num += 1
end

# break stops the looping
[1,2,3].each {|a| puts a; break if a == 2 }

# next skips to the next element
[1,2,3].each {|a| next if a == 2; puts a }

5.times do |i|
  puts i
end



# coding conventions
#
#  spaces rather than tabs
#  two spaces indentantion (but use the tab key)
#  variable and method names should be snake_cased and lowercase

vader(false)
# leave off parentheses if you don't call an argument
vader()

# this is bad!!
vader (false)

# generally use parentheses when passing arguments to methods
vader false
vader(false)

puts("hello world")
puts "hello world"

# don't do this
def method no_parentheses

end

# do this
def method(parentheses)

end

# methods that return true/false end in a question mark
1.odd?

# methods that change the object you're calling end in a bang !
string = "london"

# this just returns a capitalized string
capital_string = string.capitalize

puts string

# wheraes this modifies the string we call the method on
string.capitalize!

puts string
puts capital_string

def pope_a_catholic?
  true
end

puts pope_a_catholic?

def change_something!
  # change our object
end

# try making an array with 10 elements and only printing the odd elements
#  see how many ways you can do this
# hint there is a method called odd?