Modeling Item Size in Rails App - ruby-on-rails

Question

I have an Item model, that can be clothing, shoes, or bags (category).
I also have the Size model, that represents the Size of the Item.
The issue is:
For clothing, size can be: XS, S, M, L, XL
For shoes, size can be: 9, 9.5, 10, 10.5
Also, the shoe size depends if it is UK or US or European, so a UK 6 is a US 7 and European 40.
How should I model this?
Everything as a single Size model?
Should I have child models?
Or should I have many different models (ShoeSize, ClothingSize)?
Thanks in advance.

Answer 1

Is there any reason you require an 'Item' catch-all model?
The two ways I might do this are:
1) I would either have separate models for clothes, shoes and bags. Each model would have it's own individual size attribute.
I would also do their size attributes as a collection with "US 6" etc as separate options.
or
2) If you want to keep them all under one 'Item' model . Make their type (i.e. shoes, clothes, bags) an enumeration (Example included below). Then I would make a different column in my table for each type of size for example: Item would have an attribute that is :clothes_size that is a collection with your S,M,L,XL and then a :shoes_size with it's own selection etc.Then you can just display the field that is necessary for that item.
Enumerations look like this:
class Item < ActiveRecord::Base
enum type: [:shoes, :clothing, :bags]
end
What the enumeration will do is make it so you have an attribute to put them into categories; mapping each one to an integer in the db. (0=shoes, 1=clothing, 2=bags)
Then you will need to run a migration.
rails g migration AddTypeToItem type:integer
It will also auto generate a bunch of super cool built in methods for you to sort and find your objects by type, such as
#item.shoes? etc. Read more about them in the Rails API.

Answer 2

You could put the item category as an enumeration as #ChiefRockaChris suggested, then I would do this:
make the size attribute an integer and map these integers to a different set of strings according to item category. I would come up with a standard measurement unit for shoe size (like mm) then have another function that maps that measurement to UK, US or European.
This code would go in your Item class
def self.sizes
{
clothing: {1: 'XS', 2: 'S', 3: 'M', 4: 'L', 5: 'XL'},
shoe: {1: '35mm', 2: '40mm', 3: '45mm'}
}
end
def self.shoes_size_type
{
UK: {'35mm' => '6', '40mm' => '7', '45mm' => '8'},
US: {'35mm' => '7', '40mm' => '8', '45mm' => '9'},
Europe: {'35mm' => '35', '40mm' => '40', '45mm' => '45'}
}
end
def self.size_parsed
sizes[category][size]
end
def self.shoe_size(country)
shoe_size_type[country][size_parsed] or size_parsed
end