Ruby Cheatsheet

Basic Methods

Multiply (Easy)

Write a method that you can multiple two numbers (x,y). Test with the following examples:

• 4, 2
• 0, 4
• 900, 32
• 29999, 0

def multiply(x, y)
  return x * y
end

puts multiply(4,2)
puts multiply(0, 4)
puts multiply(900, 32)

Divide (Easy, with a special case)

Write a method that you can divide two numbers (x,y). If the denominator is zero, set it to the numerator (so that the method returns one). Test with the following examples:

• 4, 2
• 0, 4
• 900, 32

def divide(x, y)
  if(y == 0) 
    y = x
  end
  return x / y
end

puts divide(4,2)
puts divide(0, 4)
puts divide(900, 32)

Print Name

Write a method that takes a parameter (name) and greets that user.

def greet name
  return "Hello #{name}, you rock!"
end

puts greet "phybernightmare"

Smallest Number

Write a method that evaluates two numbers and returns the smallest. If the numbers are the same, it should return a message stating so.

def smallest_number(x, y)
  smallest = x

  if x == y
    smallest = "They are the same"
  elsif y < x
    smallest = y
  end

  smallest

end

puts smallest_number(400,2)

String Reverse

Write a method that accepts a string and returns the characters in reverses order.

Hint: Look at the Ruby documentation.

def reverse(string)
  # use the built in method for reversing strings
  # see http://ruby-doc.org/core/classes/String.html#M001170
  string.reverse
end

test_string = "Praxis Program"
puts reverse(test_string)

Loops

While Loop

Write a method that uses a while loop to count from 1 to 1000 and print the number of the current iteration to the screen. (That is, the first time through, the loop should print “1”; “2” the next time through; and so forth.)

def count(limit)
  counter = 0
  # note that do is optional with the while loop
  while counter <= limit
    puts counter
    counter += 1
  end
end

count(1000)

Until Loop

Write a method that uses an until loop to print each number from 0 to 5.

def count(limit)
  counter = 0
  until counter > limit
    puts counter
    counter += 1
  end
end

count(5)

For Loop

Write a method that uses a for loop to print each number from 1 to 10.

def count(limit)
  counter = 0
  for counter in (1..limit)
    puts counter
  end
end

count(10)

Times Loop

Write a method that uses a times loop to print each number from 0 to 10.

def count(limit)
  limit.times do |counter|
    puts counter
  end
end

count(11)

Classes

Write a simple class that defines a person with attributes of first_name, last_name and has a method signature of to_s which prints the object as “Jefferson, Thomas”.

class Person

  def initialize(fname, lname)
    @first_name = fname
    @last_name = lname
  end

  def to_s
    @last_name + ", " + @first_name
  end
end

tj = Person.new("Thomas", "Jefferson")
puts tj # note, puts calls to_s if it is availabe

Can’t Get Enough?

Can’t get enough? Work through the Learn Ruby the Hard Way exercises and/or implement the last programming exercises as Objects.