# Initial Rev<\/span><\/div># machine.rb<\/span><\/div>class<\/span> Machine<\/span><\/div> def<\/span> initialize<\/span>(<\/span>name<\/span>)<\/span><\/div> @name<\/span> =<\/span> name<\/span><\/div> end<\/span><\/div> <\/div>
def<\/span> device<\/span><\/div> Lot<\/span>.<\/span>find_by_tester<\/span>(<\/span>@name<\/span>)<\/span>.<\/span>device<\/span><\/div> end<\/span><\/div>end<\/span><\/div> <\/div>
# 2nd Rev - Where we build a class method that will build <\/span><\/div># an instance method.<\/span><\/div># machine.rb<\/span><\/div>class<\/span> Machine<\/span><\/div> def<\/span> initialize<\/span>(<\/span>name<\/span>)<\/span><\/div> @name<\/span> =<\/span> name<\/span><\/div> end<\/span><\/div> <\/div>
def<\/span> self<\/span>.<\/span>associated_to<\/span>(<\/span>attr<\/span>)<\/span><\/div> class_eval<\/span> %Q*<\/span><\/div> def device<\/span><\/div> Lot.find_by_<\/span>#{<\/span>attr<\/span>}<\/span>(@name).device<\/span><\/div> end<\/span><\/div> *<\/span><\/div> end<\/span><\/div> associated_to<\/span> :tester<\/span><\/div>end<\/span><\/div> <\/div>
# 3rd Rev - where we move all the methods out to a module. <\/span><\/div># Note the gymnastics we need to go through to build <\/span><\/div># class methods in the module.<\/span><\/div># machine.rb<\/span><\/div>class<\/span> Machine<\/span><\/div> include<\/span> MakesAssociatedTo<\/span><\/div> associated_to<\/span> :tester<\/span><\/div>end<\/span><\/div> <\/div>
# makes_associated_to.rb<\/span><\/div>module<\/span> MakesAssociatedTo<\/span><\/div> def<\/span> initialize<\/span>(<\/span>name<\/span>)<\/span><\/div> @name<\/span> =<\/span> name<\/span><\/div> end<\/span><\/div> <\/div>
def<\/span> self<\/span>.<\/span>included<\/span>(<\/span>base<\/span>)<\/span><\/div> base<\/span>.<\/span>extend<\/span>(<\/span>ClassMethods<\/span>)<\/span><\/div> end<\/span><\/div> <\/div>
module<\/span> ClassMethods<\/span><\/div> def<\/span> associated_to<\/span>(<\/span>attr<\/span>)<\/span><\/div> class_eval<\/span> %Q?<\/span><\/div> def device<\/span><\/div> Lot.find_by_<\/span>#{<\/span>attr<\/span>}<\/span>(@name).device<\/span><\/div> end<\/span><\/div> ?<\/span><\/div> end<\/span><\/div> end<\/span><\/div>end<\/span><\/div> <\/div><\/pre><\/div>\n \n <\/div>\n\n