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Assignment 04 Ruby Methods Classes and Blocks

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Mary Alice Moore edited this page May 8, 2024 · 1 revision

For this assignment, create a lesson4 branch. This should be done when the lesson3 branch is active.

  1. Write a method that returns in an array all the numbers between 1 and 100 that are divisible by 2 or 3 or 5. Then call the method in your program and print out what it returns. Call the program divisible.rb.

  2. Write a program hangman.rb that contains a function called hangman. The function's parameters are a word and an array of letters. It returns a string showing the letters that have been guessed. Call the function several times from within your program, testing with different words and strings, and printing out what is returned, so that you know that your hangman function works.

    Example: hangman("bob",["b"]) should return "b_b"
    Example: hangman("alphabet",["a","h"]) should return "a__ha___"

  3. Write a program that collects 5 keys and 5 values from the user, and stores them in a hash. Write a function that accepts the hash as a parameter and prints out an array of keys and an array of values. Call the function within your program so you know it works. (Question: Can you find online information on Ruby hash methods that will help with this function?) Call this program hash_to_array.rb.

  4. Create a program sums.rb with two classes.

    (a) a class called Sum1 with an initialize method that takes two parameters and sets the instance variable @total to the sum of the two. Include a line at the top of the class:

    attr_accessor :total

    (b) a class called Sum2 with an initialize method that takes two parameters a and b and sets the instance variable @a to the parameter a and the instance variable @b to the parameter b. Create a method new_total inside Sum2 that returns the sum of the instance variables @a and @b.

    (c) In the mainline program, create instances of Sum1 and Sum2, passing 5 and 6 as parameters on the new statement. Print out the total for Sum1. Print out the new_total for Sum2.

  5. The ruby array sort method can use a block to sort various arrays. The block must compare between two elements of the array, a and b. If a<b, it should evaluate to -1. If a==b, it should evaluate to 0. And if a>b, it should evaluate to 1. Here is the start of a program, which you should call sort_blocks.rb.

    class Book
  attr_reader :author, :title, :count
  def initialize(author,title,count)
    @author = author
    @title = title
    @count = count
  end
  def to_s
    "author: #{author} title: #{title} count: #{count}"
  end
end

book_array = []
book_array.push(Book.new("Beatrice Potter","Peter Rabbit",25))
book_array.push(Book.new("Henry Fielding","Tom Jones",12))
book_array.push(Book.new("Bob Woodward","All the President's Men",30))

puts "Sorting alphabetically by author"

new_array = book_array.sort do |a,b|
author1 = a.author.downcase
author2 = b.author.downcase
author1 <=> author2
# if author1 > author2
#   1
# elsif author1 < author2
#   -1
# else
#   0
# end
end
puts new_array

    Note the use of the spaceship operator <=>. It does what the commented out lines do, but on one line.

    Add to this program. Add additional calls to book_array.sort that pass blocks. For your first call to sort, pass a block so that the array is sorted in order of title, and print out the array. For your second call to sort, pass a block so that the array is sorted in order of copies, and print out the array.

  6. Create a program block_function.rb. It should have a function do_calc that calls a block using a yield statement. The yield statement will pass the numbers 7 and 9 to a block, and then do_calc will print out the result returned by the yield. Call the do_calc function twice in your program. The first time, pass a block that adds the two numbers. The second time, pass a block that multiplies the two numbers. Your program should print out 16 and 63.

  7. Using a gem: To use a gem, you need a Gemfile. This is a list of the gems your program requires, so that others can run your program. While in the directory for this repository, type the following:

    bundle init
bundle add faker

    The first line above creates the Gemfile. The second installs a gem called faker and adds a reference to the gem in the Gemfile. Others who run your program can do "bundle install" to install the same gems used by your program. The faker gem is used for testing, in that it can generate random names, phone numbers, email addresses, passwords, and so on for use in a test scenario.

    Write a program called chuck_norris_facts.rb. It should have a loop that prompts the user whether they want to know a fact about Chuck Norris. If so, it displays a random Chuck Norris fact, and then prompts the user again. If the user declines, the program exits. You use the ChuckNorris module of the faker gem. The documentation for faker is here. In order to have access to the faker gem, you need to have the following line in your program:

    require 'faker'

    The following line prints out a Chuck Norris fact:

    puts Faker::ChuckNorris.fact

    The modules comprising the Faker gem are organized into namespaces. The ChuckNorris module is within the Faker module, which is the meaning of the "::" above. Complete and try your program.

Submitting Your Work

As usual, you add, commit, and push your changes. In this case you are pushing the lesson4 branch. Then you create a pull request for the lesson4 branch, and submit a link to the pull request with your homework.

Clone this wiki locally