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(this assignment is in beta mode! let us know asap if you find mistakes or have questions in this description.)

###Overview

This homework assignment asks you to create two files (a module and a class) that are needed to run the two command lines applications you are given.

###Installing Basic HW files

To install the files needed to start this homework project, you must do:

$ git clone https://github.com/ISS-SOA/FlipFlap_HW.git

This will create a directory called FlipFlap_HW in your current directory.

###Files Given

You are given two complete code files: tsv_to_yml.rb and yml_to_tsv.rb. These files are command line applications that convert TSV and Yaml files. However, they require two more more code files that you must create in this assignment: flip_flap.rb and tsv_buddy.rb.

You are also given two data files to play with: survey.tsv and survey.yml

###Assignment:

Your task is to get tsv_to_yml.rb and yml_to_tsv.rb to work, without making any modifications to these files. Please study their code now.

They both require a file called flip_flap.rb that should contain a class called FlipFlap. On of your tasks is to create a complete class FlipFlap. However, to complete FlipFlap, you must first create a complete module called TsvBuddy in a file called tsv_buddy.rb

This file already contains an instance variable called @data that will contain a data structure to hold information loaded from TSV files. For example, you may want to make this data strcuture an Array of Hashes that looks something like this:

[{"date"=>"9/12/2014 20:20:55",
  "student_id"=>"3452",
  "languages"=>"Java, C , HTML , JavaScript , ",
  "best_language"=>"Java",
  "app_experience"=>"Native GUI applications, Database Driven Applications",
  "tech_experience"=>
   "Unix-based OS, Database"},

      <more hashes here>

]

You must fill out two methods:

def take_tsv(tsv) : this method should take a String called tsv and convert it into a data structure to store in @data.

def to_tsv : this method should take any data in @data and return a String in TSV format.

Note that modules cannot be made into object instances (i.e., you cannot do mymod = TsvBuddy.new. So to test this module while you are developing it, you can do something like this:

  class Tester
    include TsvBuddy
  end

  t = Tester.new.take_tsv(File.read('./data/survey.tsv'))

That should show you if take_tsv is creating the right structure for example.

This class should mixin (using include) TsvBuddy. That will give it access to TsvBuddy's @data member variable and to its two methods take_tsv and to_tsv.

This class should then implement two methods (not provided):

def take_yaml(yml) : this method takes a Yaml string and create a data structure to put into @data. You should be able to do this with one line of code using the yaml library's load method.

def to_yaml : this method should return @data in Yaml format.

And that's it!

If your solution works, then you should be able to convert TSV files into Yaml, and back into TSV with no change in information.

For example, here is some command line code to make sure your solution works:

$ ruby tsv_to_yml.rb data/survey.tsv data/test.yml
$ diff data/survey.yml data/test.yml

The diffcommand checks if two files are the same or not. If your code is working, the diff command should not return any information!

Similarly:

$ ruby yml_to_tsv.rb data/survey.yml data/test.tsv
$ diff data/survey.tsv data/test.tsv

This assignment shows you the power of mixins in Ruby's object model. You have created a class (FlipFlap) that can in the future incorporate code to parse or create any kind of data format (CSV, Excel, etc.). To keep FlipFlap short and uncomplicated, we can make modules (like TsvBuddy) for other formats (CsvBuddy, ExcelBuddy, etc.) and simply include them into FlipFlap. This cleanly seperates our code by keeping the logic for parsing (the XyzBuddy modules) away from the code needed by applications to handle the data (class FlipFlap).

Feel free to ask more questions on our Canvas board, and we will of course discuss this in class!