Mercurial > repos > other > SevenLanguagesInSevenWeeks
annotate 1-Ruby/acts_as_csv_module.rb @ 27:2ea3b5e9b41b
Implement day 3 self-study extensions:
* `each` method to iterate over rows
* `method_missing` to handle ".header_name" as value retrieval
| author | IBBoard <dev@ibboard.co.uk> |
|---|---|
| date | Tue, 05 Sep 2017 20:24:03 +0100 |
| parents | d50ff917c163 |
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| rev | line source |
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| 24 | 1 #--- |
| 2 # Excerpted from "Seven Languages in Seven Weeks", | |
| 3 # published by The Pragmatic Bookshelf. | |
| 4 # Copyrights apply to this code. It may not be used to create training material, | |
| 5 # courses, books, articles, and the like. Contact us if you are in doubt. | |
| 6 # We make no guarantees that this code is fit for any purpose. | |
| 7 # Visit http://www.pragmaticprogrammer.com/titles/btlang for more book information. | |
| 8 #--- | |
| 9 module ActsAsCsv | |
| 10 def self.included(base) | |
| 11 base.extend ClassMethods | |
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12 # The book doesn't do this, but it is possible to add the methods |
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13 # without having the inheriting class call a second function to do it |
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14 base.acts_as_csv |
| 24 | 15 end |
| 16 | |
| 17 module ClassMethods | |
| 18 def acts_as_csv | |
| 19 include InstanceMethods | |
| 20 end | |
| 21 end | |
| 22 | |
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23 module InstanceMethods |
| 24 | 24 def read |
| 25 @csv_contents = [] | |
| 26 filename = self.class.to_s.downcase + '.txt' | |
| 27 file = File.new(filename) | |
| 28 @headers = file.gets.chomp.split(', ') | |
| 29 | |
| 30 file.each do |row| | |
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31 csv_row = CsvRow.new(headers, row.chomp.split(', ')) |
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32 @csv_contents << csv_row |
| 24 | 33 end |
| 34 end | |
| 35 | |
| 36 attr_accessor :headers, :csv_contents | |
| 37 def initialize | |
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38 read |
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39 end |
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40 |
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41 def each(&block) |
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42 @csv_contents.each { |row| block.call row } |
| 24 | 43 end |
| 44 end | |
| 45 end | |
| 46 | |
| 47 class RubyCsv # no inheritance! You can mix it in | |
| 48 include ActsAsCsv | |
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49 # Also, nothing to do beyond the "include" - it automatically defines the methods! |
| 24 | 50 end |
| 51 | |
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52 class CsvRow |
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53 attr_reader :values |
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54 |
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55 def initialize(headers, values) |
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56 @values = Hash[headers.zip(values)] |
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57 end |
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58 |
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59 def method_missing(methId, *args) |
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60 str = methId.id2name |
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61 if @values.key?(str) |
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62 return @values[str] |
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63 else |
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64 super.method_missing(methId) |
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65 end |
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66 end |
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67 end |
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68 |
| 24 | 69 m = RubyCsv.new |
| 70 puts m.headers.inspect | |
| 71 puts m.csv_contents.inspect | |
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72 # Show the "each" method |
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73 m.each { |row| puts row.inspect } |
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74 # Use method_missing to implement heading-as-a-method |
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75 puts m.csv_contents[0].country |
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76 # And show that we still get normal failure behaviour |
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77 puts m.csv_contents[0].Country |
| 24 | 78 |