aux codes

Way back when, when I was learning database development, a mentor of mine showed me a technique that he liked to use to consolidate similar enumeration-esque database tables.

Often, applications have enumeration-esque tables that merely store simply key / value pairs, typically a unique ID and a string. Take for instance, a genders table:

[  genders   ]
[id]    [name]
1       Male
2       Female

That's a bit of a waste of a table, especially if your application has TONS of tables just like this. There's where aux codes (or auxilary codes) come in!

[  aux_codes  ]
[id]   [category_id]   [name]
1      0               Genders    <--- this defines a 'table' (because category_id = 0)
2      1               Male       <--- these are under category_id 1 (Genders)
3      1               Female
4      0               Colors     <--- defines a color 'table'
5      4               Red        <--- category_id 4 = 'Colors', so this is a color
6      4               Blue

Simple, eh?

Now, this is great, but this might get in the way of our business logic or it might dirty up our code. We don't want to always be using the AuxCode object with complex queries ... we probable want a Gender object that behaves just like it would with a full-blown genders table.

Gender = AuxCode.category('Gender').aux_code_class

# the Gender class is a full-blown ActiveRecord class
# that should behave as if there's actually a `genders` table!

Gender.find_by_name 'Male'

Gender.find_or_create_by_name 'Female'

Gender.create :name => 'Female'

male = Gender.new :name => 'Male'
male.save

Gender.find :conditions => ['name = ?', 'Male']

Gender.count

Gender.codes
Gender.code_names
Gender.aux_code
Gender.aux_codes

If you want to create all of these classes at once, as constants:

AuxCode.create_classes!

You can also access codes with a Hash-like syntax

AuxCode['Genders']['Male']
AuxCode[:Genders][:Female]

Gender[:Male]

Or with an Indifferent Hash-like syntax

AuxCode.genders['Male']
AuxCode.genders[:Male]
AuxCode.genders.male

Gender.male

# these all return the same result
Breed.find_by_name 'Golden Retriever'
Breed['Golden Retriever']
Breed[:golden_retriever]
Breed.golden_retriever
AuxCodes.breeds.golden_retriever

Read the spec to see other usage examples

TODO

• make a spec specifically for showing off the different API features quickly and easily
• convert this README to RDoc
• make table name and column names configurable (but with strong defaults)
• staticly typed fields?

NOTES

this implementation is for ActiveRecord only! i hope to eventually make a similar DataMapper implementation