ruby-on-rails - 如何验证至少一个嵌套对象的存在？

Question

代码

class Survey < ApplicationRecord
    has_many :questions, inverse_of: :survey,  :dependent => :destroy
    accepts_nested_attributes_for :questions
    validates_associated :questions
end

class Question < ApplicationRecord
    belongs_to :survey, inverse_of: :questions
    validates_presence_of :survey
end

我的调查 Controller

def new
    @survey = Survey.new
    2.times {@survey.questions.build}
end

表单

    <%= form_for @survey do |f|%>
        <p>
            <%= f.label :name%>
            <%= f.text_field :name%>
        </p>
        <%= f.fields_for :questions do |builder|%>
            <p>
                <%= builder.text_area :content, rows: 3%>   
            </p>
        <% end %>

        <p><%= f.submit %></p>

    <% end %>

如您所见，当用户创建调查时，表单会提供两个问题，我希望用户在创建调查时至少提供一个问题。怎么实现？？？

Answer 1

你可以只测试数组的长度，然后简单地做:

validates :questions, length: {minimum: 1, message: 'should have at least 1 question defined.'}