phoward8020/using-polymorphic.md

## using-polymorphic.md

      
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              using-polymorphic.md
            
          
    Creating new records with polymorphic associations

Step One - Begin with the end in mind:

checkins.create({note:"This is another test"})

Our ultimate goal is to create a checkin record, so start there.
Step Two: Create link to the polymorphable model:

Location.first.checkins.create({note: "This is another test"})

Chain the code from Step One to an existing instance of one
of the available polymorphable models (either Event or Location, in this case).
Step Three: The tricky part (aka, "WTF does '<<' mean??")

user.checkins << Location.first.checkins.create({note: "This is another test"})

Per section 4.3.1 of the Active Record Associations RailsGuide,

When you declare a has_and_belongs_to_many association, the declaring class automatically gains 16 methods related to the association:

...
collection<<(object, ...)
...