Everything in ruby is an object

Write/Read file

write_handler = File.new("newfile.out", "w")
write_handle.puts("sometext").to_s
write_handle.close
data_from_file = File.read("newfile.out")
puts "Data from file: " + data_from_file

Comments

=begin
my comments
=end

# Comments

if-else condition

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if (xxx)
    puts...
elsif (xxx)
    puts...
else
    puts...
end

Comparision

puts "5 <=> 10 = " + (5 <=> 10).to_s

Loop

loop do
    x += 1

    next unless (x%2) == 0
    puts x

    break if x >= 10
end

while y <= 10   # until y <= 10
    xxx
end

for num in nums
    puts "# {num} , " # print - no new line
end

Array

arr = ["a", "b", "c"]
arr = Array.new
arr = Array.new(5, "a")

arr.each do |str|
    puts "Get a string #{str}"
end

(0..5).each do |i|
    puts "#{i}"
end

Hash

number_hash = {"PI" => 3.14, "e" => 2.718}
puts number_hash["PI"]

Functions (pass by value)

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def add_num(num_1,num_2)
    return num_1.to_i + num_2.to_i
end

Exception

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age = 12
def check_age (age)
    raise ArgumentError, "Enter pos number" unless age > 0
end

begin
    check_age(-1)

rescue ArgumentError
    puts "Impossible age"
end

tring

mystr.upcase
mystr.downcase
mystr.swapcase
mystr.chop # remove last char
mystr.chomp('ab') # remove ab from last
mystr.delete("a") # delete every a
arr = mystr.split(/ /) # split by space

Symbol: Strings that can’t be changed

:mysymbl

Arithmetic Operators

puts "1 + 1 = " + (1+1).to_s

Define float (14 digits)

num = 1.000

ref http://www.newthinktank.com/2015/02/ruby-programming-tutorial/