Make changes for ActiveRecord

README.md

@@ -33,7 +33,7 @@ serialization.
 require "attribute_helpers"
 
 class Vehicle < ActiveRecord::Base
-  extend AttributeHelpers
+  prepend AttributeHelpers
 
   attr_class :manufacturer
   attr_symbol :status
@@ -51,7 +51,8 @@ car.status # :parked (the symbol) rather than "parked" (the string)
 
 Note: while this gem was written to help with ActiveRecord
 objects, it has **no dependencies** and works great with any database
-backend (or none!). **You can extend it in pure Ruby classes just fine!**
+backend (or none!). **You can prepend it into pure Ruby classes just
+fine!**
 
 ## Contributing
 

attribute_helpers.gemspec

@@ -24,4 +24,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "codeclimate-test-reporter", "~> 0.4"
   spec.add_development_dependency "rake", "~> 10.0"
   spec.add_development_dependency "rspec", "~> 3.1"
+  spec.add_development_dependency "temping", "~> 3.2"
 end

lib/attribute_helpers.rb

@@ -6,48 +6,59 @@
 # the database and your application code.
 
 module AttributeHelpers
-  # Marks attributes as storing symbol values, providing setters and getters for
-  # the attributes that will allow the application to use them as a symbols but
-  # store them internally as strings.
-  # @param attrs [*Symbol] a list of the names of attributes that store symbols
-  def attr_symbol(*attrs)
-    attrs.each do |attr|
-      # Store the original methods for use in the overwritten ones.
-      original_getter = instance_method(attr)
-      original_setter = instance_method("#{attr}=")
+  # This module needs to be prepended to work in ActiveRecord classes. This is
+  # because ActiveRecord doesn't have accessors/mutators defined until an
+  # instance is created, which means we need to use the prepend + super()
+  # pattern because attempts to use instance_method + binding will fail since
+  # instance_method will not find the method in the class context as it will not
+  # exist until it is dynamically created when an instance is created. Prepend
+  # works for us because it inserts the behavior *below* the class in the
+  # inheritance hierarchy, so we can access the default ActiveRecord accessors/
+  # mutators through the use of super().
+  # More information here: http://stackoverflow.com/a/4471202/1103543
+  def self.prepended(klass)
+    # We need to store the module in a variable for use when we're in the class
+    # context.
+    me = self
 
-      # Overwrite the accessor.
-      define_method attr do
-        val = original_getter.bind(self).call
-        val && val.to_sym
-      end
+    # Marks attributes as storing symbol values, providing setters and getters
+    # for the attributes that will allow the application to use them as symbols
+    # but store them internally as strings.
+    # @param attrs [*Symbol] a list of the attributes that store symbols
+    klass.define_singleton_method :attr_symbol do |*attrs|
+      # Overwrite each attribute's methods.
+      attrs.each do |attr|
+        # Overwrite the accessor.
+        me.send(:define_method, attr) do
+          val = super()
+          val && val.to_sym
+        end
 
-      # Overwrite the mutator.
-      define_method "#{attr}=" do |val|
-        original_setter.bind(self).call(val && val.to_s)
+        # Overwrite the mutator.
+        me.send(:define_method, "#{attr}=") do |val|
+          super(val && val.to_s)
+        end
       end
     end
-  end
 
-  # Marks attributes as storing class values, providing setters and getters for
-  # the attributes that will allow the application to use them as a classes but
-  # store them internally as strings.
-  # @param attrs [*Symbol] a list of the names of attributes that store classes
-  def attr_class(*attrs)
-    attrs.each do |attr|
-      # Store the original methods for use in the overwritten ones.
-      original_getter = instance_method(attr)
-      original_setter = instance_method("#{attr}=")
-
-      # Overwrite the accessor.
-      define_method attr do
-        val = original_getter.bind(self).call
-        val && Kernel.const_get(val)
-      end
+    # Marks attributes as storing class values, providing setters and getters
+    # for the attributes that will allow the application to use them as classes
+    # but store them internally as strings.
+    # @param attrs [*Symbol] a list of the attributes that store classes
+    klass.define_singleton_method :attr_class do |*attrs|
+      # Overwrite each attribute's methods.
+      attrs.each do |attr|
+        # Overwrite the accessor.
+        # @raise [NameError] if the string can't be constantized
+        me.send(:define_method, attr) do
+          val = super()
+          val && Kernel.const_get(val)
+        end
 
-      # Overwrite the mutator.
-      define_method "#{attr}=" do |val|
-        original_setter.bind(self).call(val && val.to_s)
+        # Overwrite the mutator.
+        me.send(:define_method, "#{attr}=") do |val|
+          super(val && val.to_s)
+        end
       end
     end
   end

lib/attribute_helpers/version.rb

@@ -1,3 +1,3 @@
 module AttributeHelpers
-  VERSION = "0.1.0"
+  VERSION = "0.1.1"
 end

spec/active_record_class_spec.rb

@@ -0,0 +1,98 @@
+require "spec_helper"
+
+RSpec.context "in an ActiveRecord class" do
+  Temping.create :active_record_test_class do
+    with_columns do |t|
+      t.string :symbol_attr
+      t.string :class_attr
+    end
+
+    prepend AttributeHelpers
+
+    attr_symbol :symbol_attr
+    attr_class :class_attr
+  end
+
+  let(:test_obj) { ActiveRecordTestClass.new }
+
+  describe ".attr_symbol" do
+    describe "getter" do
+      it "translates string to symbol" do
+        # Give it an intial value to be read.
+        test_obj[:symbol_attr] = "example"
+
+        expect(test_obj.symbol_attr).to eq :example
+      end
+
+      it "reads nil correctly" do
+        # Explicitly set the attribute to nil, though it's already nil by
+        # default.
+        test_obj[:symbol_attr] = nil
+
+        expect(test_obj.symbol_attr).to be_nil
+      end
+    end
+
+    describe "setter" do
+      it "translates symbol to string" do
+        test_obj.symbol_attr = :example
+        expect(test_obj[:symbol_attr]).to eq "example"
+      end
+
+      it "stores nil when nil is passed" do
+        # Give it an intial value, to make sure the nil set isn't just relying
+        # on default object behavior.
+        test_obj.symbol_attr = :example
+
+        test_obj.symbol_attr = nil
+        expect(test_obj[:symbol_attr]).to be_nil
+      end
+    end
+  end
+
+  describe ".attr_class" do
+    describe "getter" do
+      context "when string represents a real class" do
+        it "translates string to class" do
+          # Give it an intial value to be read.
+          test_obj[:class_attr] = "Object"
+
+          expect(test_obj.class_attr).to eq Object
+        end
+      end
+
+      context "when string does not represent a real class" do
+        it "raises an error" do
+          # Give it an intial value to be read.
+          test_obj[:class_attr] = "BogusClass"
+
+          expect { test_obj.class_attr }.to raise_error(NameError)
+        end
+      end
+
+      it "reads nil correctly" do
+        # Explicitly set the instance variable to nil, though it's already nil
+        # by default.
+        test_obj[:class_attr] = nil
+
+        expect(test_obj.class_attr).to be_nil
+      end
+    end
+
+    describe "setter" do
+      it "translates class to string" do
+        test_obj.class_attr = Object
+        expect(test_obj[:class_attr]).to eq "Object"
+      end
+
+      it "stores nil when nil is passed" do
+        # Give it an intial value, to make sure the nil set isn't just relying
+        # on default object behavior.
+        test_obj.class_attr = Object
+
+        test_obj.class_attr = nil
+        expect(test_obj[:class_attr]).to be_nil
+      end
+    end
+  end
+end

spec/attribute_helpers_spec.rb → spec/ruby_class_spec.rb

@@ -1,17 +1,19 @@
 require "spec_helper"
 
-RSpec.describe AttributeHelpers do
-  describe ".attr_symbol" do
-    class AttributeHelperTestClass
-      extend AttributeHelpers
+RSpec.context "in a pure Ruby class" do
+  class RubyTestClass
+    prepend AttributeHelpers
 
-      attr_accessor :symbol_attr
+    attr_accessor :symbol_attr
+    attr_accessor :class_attr
 
-      attr_symbol :symbol_attr
-    end
+    attr_symbol :symbol_attr
+    attr_class :class_attr
+  end
 
-    let(:test_obj) { AttributeHelperTestClass.new }
+  let(:test_obj) { RubyTestClass.new }
 
+  describe ".attr_symbol" do
     describe "getter" do
       it "translates string to symbol" do
         # Give it an intial value to be read.
@@ -47,22 +49,23 @@ class AttributeHelperTestClass
   end
 
   describe ".attr_class" do
-    class AttributeHelperTestClass
-      extend AttributeHelpers
-
-      attr_accessor :class_attr
-
-      attr_class :class_attr
-    end
+    describe "getter" do
+      context "when string represents a real class" do
+        it "translates string to class" do
+          # Give it an intial value to be read.
+          test_obj.instance_variable_set(:@class_attr, "Object")
 
-    let(:test_obj) { AttributeHelperTestClass.new }
+          expect(test_obj.class_attr).to eq Object
+        end
+      end
 
-    describe "getter" do
-      it "translates string to class" do
-        # Give it an intial value to be read.
-        test_obj.instance_variable_set(:@class_attr, "Object")
+      context "when string does not represent a real class" do
+        it "raises an error" do
+          # Give it an intial value to be read.
+          test_obj.instance_variable_set(:@class_attr, "BogusClass")
 
-        expect(test_obj.class_attr).to eq Object
+          expect { test_obj.class_attr }.to raise_error(NameError)
+        end
       end
 
       it "reads nil correctly" do

spec/spec_helper.rb

@@ -1,6 +1,11 @@
 require "codeclimate-test-reporter"
 CodeClimate::TestReporter.start
 
+# Connect to an in-memory database for ActiveRecord tests.
+require "temping"
+ActiveRecord::Base.
+  establish_connection(adapter: "sqlite3", database: ":memory:")
+
 require "attribute_helpers"
 
 RSpec.configure do |config|