Emmanuel Mtali Emmanuel Mtali - 1 year ago 62
Ruby Question

How to validate presence of at least one nested object?


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

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

My Surveys Controller

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


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

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

<% end %>

As you can see when user creates a survey the form provides two questions, i want user to supply at least one question when creating the survey. How can it be achieve???

Answer Source

One of the options is to use custom validation:

validate :questions_count


# or something more explicit, like `at_least_one_question` (credits to @MrYoshiji)
def questions_count
    'You can not save a survey without questions. Add at least one question'
  ) if questions.none?

Basically, the validation will be fired every time you create or "touch" (update) the survey object, and it will fail, if survey will not have at least one question associated.

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