Worksheet Week 12: Introduction to Ruby

We will be using the Hackety Hack environment (hacketyhack.net) for this, which is an easy to install Ruby environment for Windows. If you run Mac OS X or Linux at home, you can develop Ruby programs by creating them in a text file, saving them with the extension .rb and running them with:

ruby myprog.rb

1. Write a program which stores the year by year HitTastic! downloads in an array. Do not store the year in the array, just the number of downloads. Read in a year from the user, subtract 2003 from it to get an array index, and print the number of downloads for that year on the screen. To read in something from the user, use gets, e.g.

   year=gets

   Year	No. of downloads
   2003	50000
   2004	100000
   2005	200000
   2006	500000
   2007	900000
   2008	1900000

2. Create a Hit class. This should have:
   • an initialize method which has parameters for title and artist.
   • a setChart method which sets a chart position, but rejects chart positions outside the range 1-40;
   • a setYear method which sets a year, but rejects years before 1952 or after the current year (to get the current year, use Time.now.year)
   • a print method which prints out the hit.
3. Create five actual Hit objects representing the following songs:

   Chemical Brothers, Galvanize, chart 3, year 2005
   Snow Patrol, Run, chart 4, year 2004
   Electronic, Getting Away With It, chart 12, year 1989
   Genesis, Turn It On Again, chart 8, year 1980
   The X-Factor Winner, I Am The Greatest Ever, chart 1, year 2020
   

4. Write a program which stores the following information in a hash:

   Name	Room number
   Bob Backhouse	RM801
   Mark Cranshaw	RM802
   Sandra Revell	RM803
   John Flackett	RM804

   Read in a person's name from the user, and display the corresponding room number. To read in text from the keyboard, use:

   name=gets

   The variable 'name' will then contain the text read in.

Advanced

• Blocks and Iterators: Create a hash of the following student names and marks:

  Lisa 90
  James 20
  Michelle 70
  Craig 80
  Harry 60
  Tom 30
  

  Create a standalone method (outside of any class) called select_passed. This should take a parameter representing a hash, as above, and should loop through the hash. When a person with a mark of 40 or more is encountered, call yield and pass in the person's name.
  • Associate the method with a code block which simply writes out the name together with "passed!", e.g "George passed!"
  • To show the flexibility of using code blocks and iterators, call the method again, but this time associate it with a code block which simulates sending out a certificate to the user (just write out an appropriate message for now). Note how we change the code block but do not have to change the method!
• Change your answer to the hash question (Question 4) so that each value in the hash is another hash containing room number and phone number. Alter your program so that the member of staff's room number and phone number are printed out when the user enters their name.