我想使用模型中的常量动态地将实例方法声明到Concern中。
class Item < ApplicationRecord
STATES = %w(active disabled).freeze
include StatesHelper
end
module StatesHelper
extend ActiveSupport::Concern
# instance methods
self.class::STATES.each do |state|
define_method "#{state}?" do
self.state == state
end
end
end
但我得到错误:
名称错误:未初始化的常量StatesHelper::STATES
但如果我在定义的方法中使用常量,它会起作用:
module StatesHelper
extend ActiveSupport::Concern
# instance methods
def some_method
puts self.class::STATES # => ["active", "disabled"]
end
end
在我的情况下,如何使用模型中的常量?
您可以使用self.included
钩子在include时获取对include类的引用。
module StatesHelper
extend ActiveSupport::Concern
def self.included(base)
base::STATES.each do |state|
define_method "#{state}?" do
self.state == state
end
end
end
end
class Item
STATES = %w(active disabled).freeze
include StatesHelper
end
item = Item.new
item.respond_to?(:active?) # => true
item.respond_to?(:disabled?) # => true