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johnlane/tom.rb

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The One Module (TOM) is an example Ruby module that demonstrates setting of module, class, class instance and instance variables for classes that include or extend the module.
# TOM : The One Module
#
# An example Ruby module that demonstrates setting of module, class, class instance
# and instance variables for classes that include or extend the module
#
# (c) John Lane 20140218
#
module Tom
extend self # makes module methods available as class and instance methods.
@moduleinstvar = "mv1" # this sets the module instance variable (unique to the module)
@@classvar = "cv1" # this sets the class variable (common to module and all classes)
# Callback when a class includes the module (which defines instance methods).
# It extends the same module so that class methods are defined
# It defines the class instance variable in the new class (an instance of 'Class')
def included(c)
c.instance_eval do
@classinstvar ||= "civ1" # define class instance variable in including class
end
c.extend self # make module (instance) methods also exist as class methods
# self.classvar = "cv2" # this sets the class variable
attr_accessor :instvar
end
# Callback when a class extends the module (which defines class methods).
# It includes the same module so that instance methods are defined
# It defines the class instance variable in the new class (an instance of 'Class')
def extended(c)
m = self # need to refer to module (self) inside block below
# executes inside the class being extended into (self = c)
unless included_modules.include? m
c.instance_eval do
@classinstvar ||= "civ2" # define class instance variable in extending class
include m unless included_modules.include? m # include is a private method of c
end
# self.classvar = "cv3" # alternate place to set the class variable (see note)
end
end
# Callback when a class that includes/extends the module is instantiated
# It defines the instance variable within the instance.
def initialize
@instvar = "iv1" # this sets @cv, the instance variable
end
# Callback when a class that includes/extends the module is inherited
# It defines the class instance variable within the inherited class
def inherited(c)
c.instance_eval do
@classinstvar ||= "civ3" # define class instance variable in inheriting class
end
end
# The methods below are accessors that can be used as both class and instance methods.
# (due to the "extend" at the top of the module. They can be used on a class that
# includes/extends the module or on an instance of such a class.
#
# Accessors for the class variable
def classvar=(v)
@@classvar = v
end
def classvar
@@classvar
end
# Accessors for the class instance variables
def classinstvar=(v)
if defined?(@classinstvar)
@classinstvar = v
elsif self.class.respond_to? :classinstvar=
self.class.classinstvar = v
else
@classinstvar = v
end
end
def classinstvar
if defined?(@classinstvar)
@classinstvar
elsif self.class.respond_to? :classinstvar
self.class.classinstvar
else
nil
end
end
end
# Notes ##############################################################################
#
# Module Instance Variable
# this is an instance variable in the scope of the module. It does not exist in any
# classes (they have class instance varaibles instead) or instances (they have
# instane variables instead)
# mv1 : Default value. Set when the module is first defined
#
# Class Variable
# this is shared between the module and all classes that include the module
# the default value is reset at every include/extend
# cv1 : Default value. Set when the module is first defined
# cv2 : Changes current value whenever module is included into a class. Commented out
# cv3 : Changes current value whenever module is extended into a class. Commented out
#
# Class Instance Variable
# this is defined when the module is included/extended into a class
# each class that includes/extends the module gets its own class instance variable
# each class that inherits such a class also gets its own class instance variable
# civ1 : set when module is included into class.
# civ2 : set when module is extended into class.
# civ3 : set when class inherits a class that includes/extends the module
#
# Instance Variable
# this is defined with a class that included/extends the module is instantiated
# iv1 : set when the instance is created.
#
#######################################################################JL20140218#####
# TOM : The One Module
#
# An example Ruby module that demonstrates setting of module, class, class instance
# and instance variables for classes that include or extend the module
#
# rspec test suite
#
# (c) John Lane 20140218
#
require_relative 'tom'
class TomIncluded; include Tom; end
class TomExtended; extend Tom; end
class InheritedA < TomIncluded; end
class InheritedB < TomIncluded; end
class InheritedC < TomExtended; end
class InheritedD < TomExtended; end
describe Tom do
it "is a module" do
Tom.class.should == Module
end
it "has a module instance variable called @moduleinstvar" do
Tom.instance_variables.should include(:@moduleinstvar)
Tom.instance_variable_get(:@moduleinstvar).should == "mv1"
end
it "has a class variable called @@classvar" do
Tom.class_variables.should include(:@@classvar)
Tom.class_variable_get(:@@classvar).should == "cv1"
end
describe "when included in a class" do
it "includes the module" do
TomIncluded.included_modules.include? Tom.should be_true
InheritedA.included_modules.include? Tom.should be_true
InheritedB.included_modules.include? Tom.should be_true
end
it "does not have an instance variable called @moduleinstvar" do
TomIncluded.instance_variables.should_not include(:@moduleinstvar)
TomIncluded.class.instance_variables.should_not include(:@moduleinstvar)
InheritedA.instance_variables.should_not include(:@moduleinstvar)
InheritedA.class.instance_variables.should_not include(:@moduleinstvar)
InheritedB.instance_variables.should_not include(:@moduleinstvar)
InheritedB.class.instance_variables.should_not include(:@moduleinstvar)
end
it "has a class variable called @@classvar" do
TomIncluded.class_variables.should include(:@@classvar)
TomIncluded.class_variable_get(:@@classvar).should == "cv1"
TomIncluded.class_variable_get(:@@classvar).should == Tom.class_variable_get(:@@classvar)
InheritedA.class_variables.should include(:@@classvar)
InheritedA.class_variable_get(:@@classvar).should == "cv1"
InheritedA.class_variable_get(:@@classvar).should == Tom.class_variable_get(:@@classvar)
InheritedB.class_variables.should include(:@@classvar)
InheritedB.class_variable_get(:@@classvar).should == "cv1"
InheritedB.class_variable_get(:@@classvar).should == Tom.class_variable_get(:@@classvar)
end
it "has a class instance varaible called @classinstvar" do
TomIncluded.instance_variables.should include(:@classinstvar)
TomIncluded.instance_variable_get(:@classinstvar).should == "civ1"
InheritedA.instance_variables.should include(:@classinstvar)
InheritedA.instance_variable_get(:@classinstvar).should == "civ3"
InheritedB.instance_variables.should include(:@classinstvar)
InheritedB.instance_variable_get(:@classinstvar).should == "civ3"
end
it "doesn't change the module variable's value" do
Tom.instance_variable_get(:@moduleinstvar).should == "mv1"
end
it "has a class variable accessor called classvar" do
TomIncluded.methods.should include(:classvar)
TomIncluded.classvar.should == "cv1"
InheritedA.methods.should include(:classvar)
InheritedA.classvar.should == "cv1"
InheritedB.methods.should include(:classvar)
InheritedB.classvar.should == "cv1"
end
it "has a class variable accessor called classvar=" do
TomIncluded.methods.should include(:'classvar=')
InheritedA.methods.should include(:'classvar=')
InheritedB.methods.should include(:'classvar=')
end
it "has a class instance variable accessor called classinstvar" do
TomIncluded.methods.should include(:classinstvar)
TomIncluded.classinstvar.should == "civ1"
InheritedA.methods.should include(:classinstvar)
InheritedA.classinstvar.should == "civ3"
InheritedB.methods.should include(:classinstvar)
InheritedB.classinstvar.should == "civ3"
end
it "has a class instance variable accessor called classinstvar=" do
TomIncluded.methods.should include(:'classinstvar=')
InheritedA.methods.should include(:'classinstvar=')
InheritedB.methods.should include(:'classinstvar=')
end
end
describe "when extended in a class" do
it "includes the module" do
TomExtended.included_modules.include? Tom.should be_true
InheritedC.included_modules.include? Tom.should be_true
InheritedD.included_modules.include? Tom.should be_true
end
it "does not have an instance variable called @moduleinstvar" do
TomExtended.instance_variables.should_not include(:@moduleinstvar)
TomExtended.class.instance_variables.should_not include(:@moduleinstvar)
InheritedC.instance_variables.should_not include(:@moduleinstvar)
InheritedC.class.instance_variables.should_not include(:@moduleinstvar)
InheritedD.instance_variables.should_not include(:@moduleinstvar)
InheritedD.class.instance_variables.should_not include(:@moduleinstvar)
end
it "has a class variable called @@classvar" do
TomExtended.class_variables.should include(:@@classvar)
TomExtended.class_variable_get(:@@classvar).should == "cv1"
TomExtended.class_variable_get(:@@classvar).should == Tom.class_variable_get(:@@classvar)
InheritedC.class_variables.should include(:@@classvar)
InheritedC.class_variable_get(:@@classvar).should == "cv1"
InheritedC.class_variable_get(:@@classvar).should == Tom.class_variable_get(:@@classvar)
InheritedD.class_variables.should include(:@@classvar)
InheritedD.class_variable_get(:@@classvar).should == "cv1"
InheritedD.class_variable_get(:@@classvar).should == Tom.class_variable_get(:@@classvar)
end
it "has a class instance varaible called @classinstvar" do
TomExtended.instance_variables.should include(:@classinstvar)
TomExtended.instance_variable_get(:@classinstvar).should == "civ2"
InheritedC.instance_variables.should include(:@classinstvar)
InheritedC.instance_variable_get(:@classinstvar).should == "civ3"
InheritedD.instance_variables.should include(:@classinstvar)
InheritedD.instance_variable_get(:@classinstvar).should == "civ3"
end
it "doesn't change the module variable's value" do
Tom.instance_variable_get(:@moduleinstvar).should == "mv1"
end
it "has a class variable accessor called classvar" do
TomExtended.methods.should include(:classvar)
TomExtended.classvar.should == "cv1"
InheritedC.methods.should include(:classvar)
InheritedC.classvar.should == "cv1"
InheritedD.methods.should include(:classvar)
InheritedD.classvar.should == "cv1"
end
it "has a class variable accessor called classvar=" do
TomExtended.methods.should include(:'classvar=')
InheritedC.methods.should include(:'classvar=')
InheritedD.methods.should include(:'classvar=')
end
it "has a class instance variable accessor called classinstvar" do
TomExtended.methods.should include(:classinstvar)
TomExtended.classinstvar.should == "civ2"
InheritedC.methods.should include(:classinstvar)
InheritedC.classinstvar.should == "civ3"
InheritedD.methods.should include(:classinstvar)
InheritedD.classinstvar.should == "civ3"
end
it "has a class instance variable accessor called classinstvar=" do
TomExtended.methods.should include(:'classinstvar=')
InheritedC.methods.should include(:'classinstvar=')
InheritedD.methods.should include(:'classinstvar=')
end
end
describe "when instantiated" do
@ci = TomIncluded.new
@ce = TomExtended.new
instances = [@ci, @ce]
instances.each do |i|
it "has a class instance varaible called @classinstvar" do
i.class.instance_variables.should include(:@classinstvar)
end
it "has an instance varaible @instvar" do
i.instance_variables.should include(:@instvar)
end
it "has a class variable accessor called classvar" do
i.methods.should include(:classvar)
end
it "has a class variable accessor called classvar=" do
i.methods.should include(:'classvar=')
end
it "has a class instance variable accessor called classinstvar" do
i.methods.should include(:classinstvar)
end
it "has a class instance variable accessor called classinstvar=" do
i.methods.should include(:'classinstvar=')
end
it "has an instance variable accessor called instvar" do
i.methods.should include(:instvar)
end
it "has an instance variable accessor called instvar=" do
i.methods.should include(:'instvar=')
end
end
end
describe "changing the module instace variable" do
it "can be changed" do
Tom.instance_variable_set('@moduleinstvar','woohoo')
Tom.instance_variable_get('@moduleinstvar').should == 'woohoo'
Tom::instance_variable_set('@moduleinstvar','woohoo')
Tom::instance_variable_get('@moduleinstvar').should == 'woohoo'
end
end
describe "changing variable values" do
instances = [
TomIncluded.new,
TomExtended.new,
InheritedA.new,
InheritedA.new,
InheritedB.new,
InheritedB.new,
InheritedC.new,
InheritedC.new,
InheritedD.new,
InheritedD.new,
TomIncluded.new,
TomExtended.new,
InheritedA.new,
InheritedA.new,
InheritedB.new,
InheritedB.new,
InheritedC.new,
InheritedC.new,
InheritedD.new,
InheritedD.new
]
describe "changing the class variable" do
instances.each do |i|
it "can be changed" do
i.classvar = 'changed value'
i.classvar.should == 'changed value'
Tom.classvar.should == 'changed value'
TomIncluded.classvar.should == 'changed value'
TomExtended.classvar.should == 'changed value'
InheritedA.classvar.should == 'changed value'
InheritedB.classvar.should == 'changed value'
InheritedC.classvar.should == 'changed value'
InheritedD.classvar.should == 'changed value'
end
it "is the same in all classes and instances" do
Tom.classvar = 'class value'
Tom.classvar.should == 'class value'
TomIncluded.classvar.should == 'class value'
TomExtended.classvar.should == 'class value'
InheritedA.classvar.should == 'class value'
InheritedB.classvar.should == 'class value'
InheritedC.classvar.should == 'class value'
InheritedD.classvar.should == 'class value'
instances[0].classvar.should == 'class value'
instances[1].classvar.should == 'class value'
instances[2].classvar.should == 'class value'
instances[3].classvar.should == 'class value'
instances[4].classvar.should == 'class value'
instances[5].classvar.should == 'class value'
instances[6].classvar.should == 'class value'
instances[7].classvar.should == 'class value'
instances[8].classvar.should == 'class value'
instances[9].classvar.should == 'class value'
instances[10].classvar.should == 'class value'
instances[11].classvar.should == 'class value'
instances[12].classvar.should == 'class value'
instances[13].classvar.should == 'class value'
instances[14].classvar.should == 'class value'
instances[15].classvar.should == 'class value'
instances[16].classvar.should == 'class value'
instances[17].classvar.should == 'class value'
instances[18].classvar.should == 'class value'
instances[19].classvar.should == 'class value'
end
end
end
describe "changing the class instance variable" do
instances.each do |i|
it "can be changed" do
i.classinstvar = 'changed value'
i.classinstvar.should == 'changed value'
end
end
it "is unique per class" do
instances[0].classinstvar = "value TomIncluded"
instances[1].classinstvar = "value TomExtended"
instances[2].classinstvar = "value InheritedA"
instances[4].classinstvar = "value InheritedB"
instances[6].classinstvar = "value InheritedC"
instances[8].classinstvar = "value InheritedD"
instances[0].classinstvar.should == "value TomIncluded"
instances[1].classinstvar.should == "value TomExtended"
instances[2].classinstvar.should == "value InheritedA"
instances[3].classinstvar.should == "value InheritedA"
instances[4].classinstvar.should == "value InheritedB"
instances[5].classinstvar.should == "value InheritedB"
instances[6].classinstvar.should == "value InheritedC"
instances[7].classinstvar.should == "value InheritedC"
instances[8].classinstvar.should == "value InheritedD"
instances[9].classinstvar.should == "value InheritedD"
instances[10].classinstvar.should == "value TomIncluded"
instances[11].classinstvar.should == "value TomExtended"
instances[12].classinstvar.should == "value InheritedA"
instances[13].classinstvar.should == "value InheritedA"
instances[14].classinstvar.should == "value InheritedB"
instances[15].classinstvar.should == "value InheritedB"
instances[16].classinstvar.should == "value InheritedC"
instances[17].classinstvar.should == "value InheritedC"
instances[18].classinstvar.should == "value InheritedD"
instances[19].classinstvar.should == "value InheritedD"
end
end
describe "changing the instance variable" do
instances.each do |i|
it "can be changed" do
i.instvar = 'changed value'
i.instvar.should == 'changed value'
end
end
it "is unique per instance" do
(0..19).each { |i| instances[i].instvar = "value #{i}" }
(0..19).each { |i| instances[i].instvar.should == "value #{i}" }
end
end
end
end
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