问Rails模型基于控制器的应用验证

EN

class Model 
  attr_accessor :step
  validate_presence_of :name, if: { |m| m.step == 1 }
  validate_presence_of :age, if: { |m| m.step == 2 }
end

class Controller
  def first_step
    @model = Model.new(params[:model].merge(step: 1))
    if @model.valid?
   ....
  end
  def second_step
    @model.update_attributes(params[:model].merge(step: 2))
    if @model.valid?
   ....
  end
end