I finished the Ruby chapter in Seven Languages in Seven Weeks. It tries to make you familiar with the core concepts of several languages rather quickly. Dutifully I did all exercises, but most likely they can be improved to be more ruby like. I'll post my code samples one by one, so I can apply things learned in previous questions to later questions.

Previously, Day 1

Day 2

Write a simple grep that will print the lines of a file having any occurrences of a phrase anywhere in that line (in my example 'bleh'). Include line numbers.

File.open( 'grepFile.txt', 'r' ) do |file|
  lines = []
  line_number = 1
  file.readlines.each do |line|
    lines[line_number] = line
    line_number += 1
  end
  lines.each_index do |i|  
    line = lines[i]
    puts "line #{i.to_s}: #{line}" if line =~ /bleh/
  end
end

I finished the Ruby chapter in Seven Languages in Seven Weeks. It tries to make you familiar with the core concepts of several languages rather quickly. Dutifully I did all exercises, but most likely they can be improved to be more Ruby-like.

Write a simple grep that will print the lines of a file having any occurrences of a phrase anywhere in that line (in my example 'bleh'). Include line numbers.

File.open( 'grepFile.txt', 'r' ) do |file|
  lines = []
  line_number = 1
  file.readlines.each do |line|
    lines[line_number] = line
    line_number += 1
  end
  lines.each_index do |i|  
    line = lines[i]
    puts "line #{i.to_s}: #{line}" if line =~ /bleh/
  end
end

Since Day 2 was really short, I'll just add the (final) day 3 here as well.

Given: a CSV file structered with a first line with headers and subsequent rows with data.

one, two
lions, tigers

Create a module which loads the header and values from a CSV file, based on the name of the implementing class. (RubyCSV -> "rubycsv.txt") Support an each method which returns a CsvRow object. Use method_missing to return the value for the column for a given heading. E.g. usage which will print "lions":

m = RubyCsv.new
m.each { |row| p row.one }

My implementation:

class CsvRow
  attr :row_hash

  def initialize( row_hash )
    @row_hash = row_hash
  end
  
  def method_missing( name, *args )
    @row_hash[ name.to_s ]
  end
end

module ActsAsCsv
  attr_accessor :headers, :csv_contents

  def self.included( base )
    base.extend ClassMethods
  end
  
  module ClassMethods
    def acts_as_csv
      include InstanceMethods
    end
  end
  
  module InstanceMethods
    def read
      @csv_contents = []
      filename = self.class.to_s.downcase + '.txt'
      file = File.new( filename )
      @headers = file.gets.chomp.split( ', ' )
      
      file.each do |row|
        @csv_contents << row.chomp.split( ', ' )
      end
    end               
    
    def initialize
      read
    end
    
    def each      
      @csv_contents.each do |content|        
        hash = {}
        @headers.zip( content ).each { |i| hash[ i[0] ] = i[1] }
        yield CsvRow.new hash
      end
    end
  end
end

class RubyCsv  # No inheritance! You can mix it in.
  include ActsAsCsv
  acts_as_csv
end