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module ActiveRecord::Associations::Builder
class HasAndBelongsToMany < CollectionAssociation #:nodoc:
self.macro = :has_and_belongs_to_many
self.valid_options += [:join_table, :association_foreign_key, :delete_sql, :insert_sql]
def build
reflection = super
check_validity(reflection)
redefine_destroy
reflection
end
private
def redefine_destroy
# Don't use a before_destroy callback since users' before_destroy
# callbacks will be executed after the association is wiped out.
name = self.name
model.send(:include, Module.new {
class_eval <<-RUBY, __FILE__, __LINE__ + 1
def destroy # def destroy
super # super
#{name}.clear # posts.clear
end # end
RUBY
})
end
# TODO: These checks should probably be moved into the Reflection, and we should not be
# redefining the options[:join_table] value - instead we should define a
# reflection.join_table method.
def check_validity(reflection)
if reflection.association_foreign_key == reflection.foreign_key
raise ActiveRecord::HasAndBelongsToManyAssociationForeignKeyNeeded.new(reflection)
end
reflection.options[:join_table] ||= join_table_name(
model.send(:undecorated_table_name, model.to_s),
model.send(:undecorated_table_name, reflection.class_name)
)
if model.connection.supports_primary_key? && (model.connection.primary_key(reflection.options[:join_table]) rescue false)
raise ActiveRecord::HasAndBelongsToManyAssociationWithPrimaryKeyError.new(reflection)
end
end
# Generates a join table name from two provided table names.
# The names in the join table names end up in lexicographic order.
#
# join_table_name("members", "clubs") # => "clubs_members"
# join_table_name("members", "special_clubs") # => "members_special_clubs"
def join_table_name(first_table_name, second_table_name)
if first_table_name < second_table_name
join_table = "#{first_table_name}_#{second_table_name}"
else
join_table = "#{second_table_name}_#{first_table_name}"
end
model.table_name_prefix + join_table + model.table_name_suffix
end
end
end
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