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# File 'lib/mongo_mapper/plugins/counter_cache.rb', line 39
def counter_cache(association_name, options = {})
options.symbolize_keys!
field = options[:field] ?
options[:field] :
"#{self.collection_name.gsub(/.*\./, '')}_count"
association = associations[association_name]
if !association
raise InvalidCounterCacheError, "You must define an association with name `#{association_name}' on model #{self}"
end
if !association.polymorphic?
association_class = association.klass
key_names = association_class.keys.keys
if !key_names.include?(field.to_s)
_raise_when_missing_counter_cache_key(association_class, field)
end
end
after_create do
if obj = self.send(association_name)
if !obj.respond_to?(field)
self.class._raise_when_missing_counter_cache_key(obj.class, field)
end
obj.increment(field => 1)
obj.write_attribute(field, obj.read_attribute(field) + 1)
end
true
end
after_destroy do
if obj = self.send(association_name)
if !obj.respond_to?(field)
self.class._raise_when_missing_counter_cache_key(obj.class, field)
end
obj.decrement(field => 1)
obj.write_attribute(field, obj.read_attribute(field) - 1)
end
true
end
end
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