Hello all,
I'm working with a legacy schema that uses polymorphism and having some
trouble getting AR to cooperate with it's original design. Looking through
issues, I've seen a few other requests for enum based polymorphic type
columns. Personally, I'm not a huge fan of inserting model names into the
database: it just seems like an enum or table name would be more
appropriate.
Is there a built-in way to use different values for the polymorphic type
column? It seems like I can override `ActiveRecord::Base.compute_type`, but
that's kind of ugly.
I wrote up a monkey patch (using AR 4.0.13 and pretty much untested):
module ActiveRecord
module Associations
module BelongsToPolymorphicEnum
extend ActiveSupport::Concern
included do
alias_method_chain :klass, :enum
alias_method_chain :replace_keys, :enum
end
def klass_with_enum
if klass_types.nil?
klass_without_enum
else
type = klass_types.invert[owner[reflection.foreign_type]]
type.presence && type.constantize
end
end
private
def replace_keys_with_enum(record)
if klass_types.nil?
replace_keys_without_enum
else
super
owner[reflection.foreign_type] = klass_types[record.class.name]
end
end
def klass_types
options[:types]
end
end
module BuilderWithPolymorphicEnum
def valid_options
super + [:types]
end
end
Builder::BelongsTo.send :include, BuilderWithPolymorphicEnum
BelongsToPolymorphicAssociation.send :include, BelongsToPolymorphicEnum
end
end
It allows you to do this:
class Picture < ActiveRecord::Base
belongs_to :imageable, polymorphic: true, types: { 'Employee' => 1,
'Product' => 2 }
end
I'm all for conventions, but Polymorphic tables seems like an area in need
of more configuration options.
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