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Say there are three classes: A, B & C. I want each class to have a class method, say self.foo, that has exactly the same code for A, B & C.
Is it possible to define self.foo in a module and include this module in A, B & C? I tried to do so and got an error message saying that foo is not recognized.
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There are two standard approaches for defining class method in Ruby. The first one is the “def self. method” (let's call it Style #1), and the second one is the “class << self” (let's call it Style #2). Both of them have pros and cons.
You can only use private methods with:Other methods from the same class. Methods inherited from the parent class. Methods included from a module.
Discussion. You can define and access instance variables within a module's instance methods, but you can't actually instantiate a module. A module's instance variables exist only within objects of a class that includes the module.
Explanation: Yes, Module instance variables are present in the class when you would include them inside the class.
Yep
module Foo def self.included(base) base.extend(ClassMethods) end module ClassMethods def some_method # stuff end end end One possible note I should add - if the module is going to be ALL class methods - better off just using extend ModuleName in the Model and defining the methods directly in the module instead - rather than having a ClassMethods module inside the Module, a la
module ModuleName def foo # stuff end end 
module Common def foo puts 'foo' end end class A extend Common end class B extend Common end class C extend Common end A.foo Or, you can extend the classes afterwards:
class A end class B end class C end [A, B, C].each do |klass| klass.extend Common end If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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