chapter 24 examples

Author: cocoa

README.md

@@ -130,6 +130,11 @@ tree hierarchy
 │   ├── in_the_wild.rb
 │   └── magic_methods.rb
 ├── chapter_24
+│   ├── alias_method.rb
+│   ├── document.rb
+│   ├── fixing_a_broken_class.rb
+│   ├── improving_existing_classes.rb
+│   └── wide_open_classes.rb
 ├── chapter_25
 │   ├── class_methods_that_change_their_class.rb
 │   ├── document.rb
@@ -173,6 +178,6 @@ tree hierarchy
     │       └── document_spec.rb
     └── document-1.0.1.gem
 
-35 directories, 128 files
+35 directories, 133 files
 
 ```

chapter_24/alias_method.rb

@@ -0,0 +1,21 @@
+require './document.rb'
+
+# fixing the String class to allow between string and document
+class String
+
+  # it copies the method '+' giving the fresh copy the name 'old_addition'
+  alias_method :old_addition, :+
+
+  def +( other )
+    if other.kind_of? Document
+      new_content = self + other.content
+      return Document.new(other.title, other.author, new_content)
+    end
+    old_addition( other )
+  end
+end
+
+# example
+doc = Document.new('Bio','Russ',' my resume.')
+new_doc = 'This is' + doc
+puts new_doc.inspect

chapter_24/document.rb

@@ -0,0 +1,23 @@
+class Document
+  attr_accessor :title, :author, :content
+
+  def initialize(title, author, content)
+    @title = title
+    @author = author
+    @content = content
+  end
+
+  def words
+    @content.split
+  end
+
+  def word_count
+    words.size
+  end
+
+  def average_word_length
+    len = words.inject(0.0) { |total, word| word.size+total }
+    len/word_count
+  end
+  
+end

chapter_24/fixing_a_broken_class.rb

@@ -0,0 +1,18 @@
+require './document.rb'
+
+# example using the ORIGINAL method
+empty_doc = Document.new( 'Empty', 'Russ', '')
+puts empty_doc.average_word_length
+
+# fix the class before use
+class Document
+  def average_word_length
+    return 0.0 unless word_count != 0
+    total = words.inject(0.0) { |result,word| word.size + result }
+    total / word_count
+  end
+end
+
+# example using the FIXED method
+empty_doc = Document.new( 'Empty', 'Russ', '')
+puts empty_doc.average_word_length

chapter_24/improving_existing_classes.rb

@@ -0,0 +1,19 @@
+require './document.rb'
+
+# fixing the String class to allow between string and document
+class String
+  def +( other )
+    if other.kind_of? Document
+      new_content = self + other.content
+      return Document.new(other.title, other.author, new_content)
+    end
+    result = self.dup
+    result << other.to_str
+    result
+  end
+end
+
+# example
+doc = Document.new('Bio','Russ',' my resume.')
+new_doc = 'This is' + doc
+puts new_doc.inspect

chapter_24/wide_open_classes.rb

@@ -0,0 +1,38 @@
+# first definition of Document class
+class Document
+  attr_accessor :title, :author, :content
+
+  def initialize(title, author, content)
+    @title = title
+    @author = author
+    @content = content
+  end
+end
+
+
+# a Document class instance
+cover_letter = Document.new( 'Letter', 'Russ', "Here's my resume")
+
+
+# reopen the class Document to insert a new method
+class Document
+  def words
+    @content.split
+  end
+  def word_count
+    words.size
+  end
+end
+
+
+# another method
+class Document
+  def average_word_length
+    len = words.inject(0.0) { |total, word| word.size+total }
+    len/word_count
+  end
+end
+
+
+# we can use now the new method
+puts "Average word length: #{cover_letter.average_word_length}"