在Rails中将初始化方法覆盖到模型中

Question

I'm trying to override the initialize method. See below

class Restriction < ActiveRecord::Base
  RESTRICTION_TYPES = {
    less_than: "IND<X", 
    greater_than: "X<IND", 
    between: "X<IND<Y"
  }

  def initialize restriction_type_name
    super
    formula = RESTRICTION_TYPES[restriction_type_name]
  end

  private
  def formula=f
    self[:formula] = f
  end

end

When I run r = Restriction.new(:between) I get the exception:

NoMethodError: undefined method `stringify_keys' for :between:Symbol

What am I doing wrong?

BTW I'm doing this due to formula attribute can't be acceded from outside.

Answer 1

You can't override initialize , and what you have wouldnt work anyway (it would try to set a local variable called formula in the initialize method). You can, however, move the conditions into your formula= setter, so it reads like:

def formula=(restriction_type_name)
  self[:formula] = RESTRICTION_TYPES[restriction_type_name]
end