Ruby on Rails has special under-the-hood magic that will patch four methods onto your models for each enum value you specify. That means if you specify an enum with 3 values, Rails gives you 12 magic methods associated with names based on these values.
Take the example above:
def Invoice < ActiveResource
enum status: [:pending: 'pending', in_progress: 'in_progress', finished:
'finished']Rails will put 4 methods for each enum:
IN this example invoice represents an instance of a since invoice and Invoice represents the Invoice class.
for our Invoice example… | ||
| Bang (!) | Tells the object to become that status. | invoice.pending! will tell the invoice to turn its status into pending |
| Interrogative (?) | Asks the object if it is in that status | invoice.pending? returns true if the invoice is in pending status; false if not |
| Scope (…) | When used on the class, provides a scope that will get all of the object in this state | Invoice.pending will return a scope that can be used to find all of the pending invoices |
Negative scope (not_*) | Invoice.not_pending will return a scope that can be used to find all of the invoices not in pending status |
Remember, the scopes are ActiveRecord chain-able scopes, so they can be used in conjunction with other valid scopes too. (Invoices.pending.not_paid for example).