Model validation

Rails
1

I have an ‘animal’ model that has zero to many animal_options that are
other models. Some of these animal_options are mutually exclusive,
like ‘wet’ versus ‘dry’ and such. How can I validate the animal model
to only contain one of these mutually exclusive options?

Breakpointing shows me that my code in Animal.validate doesn’t get ran
before the invalid animal_options get saved to the database:

class Animal < ActiveRecord::Base

has_many :animal_animal_options
has_many :animal_options, :through => :animal_animal_options

def validate
# validate mutually exclusive options
dry = AnimalOption.find_by_name( ‘Dry’ )
wet = AnimalOption.find_by_name( ‘Wet’ )
if animal_options.include?( dry ) && animal_options.include?( wet )
errors.add( :animal_options, ‘Cannot be dry and wet at the same
time’ )
end
end

end

Another issue I’m having is how to make the options pre-selected when
editing an animal:

<%= select_tag ‘animal_option_id[]’,
options_from_collection_for_select( @animal_options, ‘id’, ‘name’,
@animal.animal_options ), { :multiple => true, :size =>
@animal_options.size } %>

I get no errors from that tag but it doesn’t pre-select anything either.

Any help would be appreciated.

–
Greg D.
http://destiney.com/

2

Greg,

I think your problem is that in the validate below the finds are
returning arrays into “dry” and “wet”. In addition, they aren’t linked
to your current Animal. Your current Animal is accessible as “self” in
the validate and since you have the relationship defined you can simply
do this:

def validate
# create array of option names associated with the current animal
options = self.animal_options.map {|option| option.name}

# Animal can't be both wet and dry
if options.include?( 'Wet' ) and options.include( 'Dry' )
   errors.add( :animal_options, 'Cannot be dry and wet at the same

time’ )
end

# Other option comparisons

end

David