Module to share methods with mulitple models

Rails
1

I am writing an in-house stock control system. I have models for
Product, Customer, and Supplier. Each of these have a method
(stock_count) to look up the number of instances each appear in the
stock list (Stock). So if I have:

customer_a = Customer.find(1)

customer_a.stock_count, returns the number of stock items assigned to
this customer. This returns the same as customer_a.stocks.length, but
I’ve added further functionality so that customer_a.stock_count(“sold”)
returns the number of items in the stock list assigned to this customer,
and whose status is sold.

At the moment each model contains the code for a stock_count method.
This isn’t DRY! I think I should create a module containing a single
definition of stock_count, rewritten so that it can be mixed into the
models. Then use “include module_name” in the models that use it.

My problem is that I don’t know where to put the module. Do I create a
file called something line stock_count_module.rb and put it in
app/models? Is there a better place to put it (e.g. /compontents, or
/lib)?

2

Rob N. wrote:

My problem is that I don’t know where to put the module. Do I create a
file called something line stock_count_module.rb and put it in
app/models? Is there a better place to put it (e.g. /compontents, or
/lib)?

OK - I’ve had a play. I created a module called StockOption by creating
a new file called “stock_option.rb” and having the first line as:

module StockOption

The rest of the file contained the method definitions, rewritten so that
they were not model specific.

I then saved this into \components. Then in each model I replaced the
methods with the single line:

include StockOption

I then ran all my unit tests to make sure this worked - it does. It also
works if I put the file in \lib. I’m still not sure where I should be
putting the file, but at least have a working solution now.

3

Lib is the place Rob.

4

James Mccarthy wrote:

Lib is the place Rob.

Thank you James. I’ve moved the module to \lib.