Add Trash (translated hash)

3 files changed, 131 insertions, 1 deletions

diff --git a/lib/hashie.rb b/lib/hashie.rb
index 06c238a..0a1e9ba 100644
--- a/lib/hashie.rb
+++ b/lib/hashie.rb
@@ -2,4 +2,8 @@ require 'hashie/hash_extensions'
 require 'hashie/hash'
 require 'hashie/mash'
 require 'hashie/dash'
-require 'hashie/clash'
\ No newline at end of file
+require 'hashie/clash'
+
+module Hashie
+  autoload :Trash, 'hashie/trash'
+end
diff --git a/lib/hashie/trash.rb b/lib/hashie/trash.rb
new file mode 100644
index 0000000..7babcca
--- /dev/null
+++ b/lib/hashie/trash.rb
@@ -0,0 +1,55 @@
+require 'hashie/dash'
+
+module Hashie
+  # A Trash is a 'translated' Dash where the keys can be remapped from a source
+  # hash.
+  #
+  # Trashes are useful when you need to read data from another application,
+  # such as a Java api, where the keys are named differently from how we would
+  # in Ruby.
+  class Trash < Hashie::Dash
+
+    # Defines a property on the Trash. Options are as follows:
+    #
+    # * <tt>:default</tt> - Specify a default value for this property, to be
+    # returned before a value is set on the property in a new Dash.
+    # * <tt>:from</tt> - Specify the original key name that will be write only.
+    def self.property(property_name, options = {})
+      super
+
+      if options[:from]
+        translations << options[:from].to_sym
+        class_eval <<-RUBY
+          def #{options[:from]}=(val)
+            self[:#{property_name}] = val
+          end
+        RUBY
+      end
+    end
+
+    # Set a value on the Dash in a Hash-like way. Only works
+    # on pre-existing properties.
+    def []=(property, value)
+      if self.class.translations.include? property.to_sym
+        send("#{property}=", value)
+      elsif property_exists? property
+        super
+      end
+    end
+
+    private
+
+    def self.translations
+      @translations ||= []
+    end
+
+    # Raises an NoMethodError if the property doesn't exist
+    #
+    def property_exists?(property)
+      unless self.class.property?(property.to_sym)
+        raise NoMethodError, "The property '#{property}' is not defined for this Trash."
+      end
+      true
+    end
+  end
+end
diff --git a/spec/hashie/trash_spec.rb b/spec/hashie/trash_spec.rb
new file mode 100644
index 0000000..38fae0d
--- /dev/null
+++ b/spec/hashie/trash_spec.rb
@@ -0,0 +1,71 @@
+require 'spec_helper'
+
+describe Hashie::Trash do
+  class TrashTest < Hashie::Trash
+    property :first_name, :from => :firstName
+  end
+
+  let(:trash) { TrashTest.new }
+
+  describe 'translating properties' do
+    it 'adds the property to the list' do
+      TrashTest.property :not_an_att, :from => :notAnAtt
+      TrashTest.properties.should include('not_an_att')
+    end
+
+    it 'creates a method for reading the property' do
+      trash.should respond_to(:first_name)
+    end
+
+    it 'creates a method for writing the property' do
+      trash.should respond_to(:first_name=)
+    end
+
+    it 'creates a method for writing the translated property' do
+      trash.should respond_to(:firstName=)
+    end
+
+    it 'does not create a method for reading the translated property' do
+      trash.should_not respond_to(:firstName)
+    end
+  end
+
+  describe 'writing to properties' do
+
+    it 'does not write to a non-existent property using []=' do
+      lambda{trash['abc'] = 123}.should raise_error(NoMethodError)
+    end
+
+    it 'writes to an existing property using []=' do
+      lambda{trash['first_name'] = 'Bob'}.should_not raise_error
+    end
+
+    it 'writes to a translated property using []=' do
+      lambda{trash['firstName'] = 'Bob'}.should_not raise_error
+    end
+
+    it 'reads/writes to an existing property using a method call' do
+      trash.first_name = 'Franklin'
+      trash.first_name.should == 'Franklin'
+    end
+
+    it 'writes to an translated property using a method call' do
+      trash.firstName = 'Franklin'
+      trash.first_name.should == 'Franklin'
+    end
+  end
+
+  describe ' initializing with a Hash' do
+    it 'does not initialize non-existent properties' do
+      lambda{TrashTest.new(:bork => 'abc')}.should raise_error(NoMethodError)
+    end
+
+    it 'sets the desired properties' do
+      TrashTest.new(:first_name => 'Michael').first_name.should == 'Michael'
+    end
+
+    it 'sets the translated properties' do
+      TrashTest.new(:firstName => 'Michael').first_name.should == 'Michael'
+    end
+  end
+end