How to call another method from a self method with ruby?

Question

# app/models/product.rb
class Product < ApplicationRecord
  def self.method1(param1)
    # Here I want to call method2 with a parameter
    method2(param2)
  end

  def method2(param2)
    # Do something
  end
end

I call method1 from controller. When I run the program. I got an error:

method_missing(at line method2(param2))
.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/activerecord-5.0.0/lib/active_record/relation/batches.rb:59:in `block (2 levels) in find_each
...

Answer 1

class Product < ApplicationRecord
  def self.method1(param1)
    # Here I want to call method2 with a parameter
    method2(param2)
  end

  def self.method2(param2)
    # Do something
  end
end

Explanation: first one is a class method, the latter was an instance method. Class methods don't need a receiver (an object who call them), instance methods need it. So, you can't call an instance method from a class method because you don't know if you have a receiver (an instanciated object who call it).

Answer 2

It does not work because method2 is not defined for Product object.

method2 is an instance method, and can be called only on the instance of Product class.