Model code to module: wrong number of args, class/ instance method?

Question

I am trying to move some model code to a module. The original model method: I am trying to move some model code to a module. The original model method: ``` class Book < ActiveRecord::Base def book_royalty(period='enddate', basis="Net receipts") #stuff end end ``` So I add ``` include Calculation ``` and move the method to a module: ``` module Calculation def book_royalty(period='enddate', basis="Net receipts") #stuff end end ``` But now I'm getting wrong number of arguments (2 for 0) This is the error I also get if I make the method in the book.rb model a class method i.e. if I make the method name `self.book_royalty(args)`. Am I inadvertently making the methods moved to the module class methods? I'm using `include` in book.rb, not `extend`. How can I get the parent model to successfully include the module's methods? Edit `book_royalty` is called in the Royaltystatement model. book.rb: ``` attr_accessor :book_royalty ``` royaltystatement.rb: ``` def initialize_arrays @royalty = [] ...…

Accepted Answer

Explanation:

Your module defines a method `book_royalty` that takes two arguments. Then, a couple of lines after the inclusion of that module you use class macro `attr_accessor` which defines two methods,

```
def book_royalty
  @book_royalty
end

def book_royalty= val
  @book_royalty = val
end
```

This effectively overwrites your `book_royalty` from the module. Now it accepts no arguments. Hence the error

wrong number of arguments (2 for 0)

when trying to execute line

```
book.book_royalty("enddate", basis)
```

You don't need `attr_accessor` or anything else in order to use a method from included module. It becomes available automatically.

Model code to module: wrong number of args, class/ instance method?

Solution

Problem