在Rails中动态创建模型的多个实例

Question

I have two related models "Test" and "Student":

class Student< ActiveRecord::Base
   has_many :tests
end

class Test< ActiveRecord::Base
   belongs_to :Student
end

What I'm trying to do is create an unknown number of tests for a student, ie from the student's show.html.erb, user may create multiple tests. Also, once a set of tests are created, user can again add any number of tests via the student's show.html.erb in the same way as before.

Please note that test creation is not part of student creation (Like it is in this railscast). Student is created separately and then multiple tests can be added from a button on app/views/students/show.html.erb.

I'm calling a custom action (customAction1 below) in the students_controller.rb when the button to add tests is clicked. What I can think of is to dynamically build and append, say 10 (for a start) instances of tests to a student's instance (in the students_controller.rb's custom action), render a custom view (addtests.html.erb below), then allow user to enter the various input fields for these test instances in that view, and finally when create button is clicked, call another custom action (customAction2 below) in the students_controller.rb to save (only the non-empty) test instances.

Is this the correct (read Rails) way to go about it? And since I'm new to rails please correct my code that does the aforementioned things:

students_controller.rb
#called when button to add tests is clicked from students/show.html.erb view:
def customAction1
    @student = Student.find(params[:student])
    10.times {@student.tests.append}
    render 'addtests'
end

addtests.html.erb
# Here I'm unable to show input fields for each of the 10 newly added tests

students_controller.rb
# Called when create button is clicked from addtests.html.erb after inputting fields for some tests
def customAction2
    @student.tests.save  # Is this correct?
    render 'show' # render show.html.erb of this student
end

If this is indeed the right approach, please let me know how to write the addtests.html.erb view.

Answer 1

You can still add the tests through the student as an update student not a create and use cocoon gem to help you with the nested forms, I'm thinking of something like this

Gemfile

gem 'cocoon'

Gem link: https://github.com/nathanvda/cocoon

models/student.rb

accepts_nested_attributes_for :tests

students_controller.rb

def show
   @student = Student.find(params[:id])
   @student.tests.build #you can check here if the student has already tests you can skip this build
end

def student_params
    #add your own student parameters before the tests attributes
    params.require(:student).permit(tests_attributes: [:id, :name, :_destroy]
end

students/show.html.haml

= form_for @student do |f|
  = f.fields_for :tests do |builder|
    = render 'tests/test_fields', f: builder
  = link_to_add_fields 'Add Tests', f, :tests

This form will submit to students#update action with the test_attributes only as parameters

tests/_test_fields.html.haml

-#add other test attributes that you might have
= f.input :name
= link_to_remove_association 'Remove Test', f

Answer 2

I ended up watching the revised version of the nested form railscast to solve the problem. Following are the steps:

students_controller.rb
#called when button to add tests is clicked from students/show.html.erb view:
def addTests
    @student = Student.find(params[:student])
    render 'addtests'
end

addtests.html.erb    
    <%= form_for(@student, url: {action: "realAddTests"}, method: :post) do |student_form| %>
      <% test1 = Test.new %> #to show fields for one test by default
      <%= student_form.fields_for(:tests, test1) do |f| %>
        <%= render('test_fields', f: f) %>
      <% end %>
      <br />
      <%= link_to_add_fields 'ADD MORE', student_form, :tests %><br /><br />
      <%= student_form.submit "Save", class: "btn btn-primary" %>
    <% end %>

_test_fields.html.erb  #partial used above
<fieldset>
    <%= f.label "Name" %>
    <%= f.number_field :name %>

    <%= f.label :date %>
    <%= f.date_field :date %>

    <%= f.label :time %>
    <%= f.time_field :time %>
</fieldset>

students_controller.rb
# Called when save button is clicked in addtests.html.erb after inputting fields for some tests  
def realAddTests
new_tests_hash = params[:student][:tests_attributes]
            new_tests_hash.each do |key, value|
                new_test_attributes = value.permit(:name, :date, :time)
                @test = Test.new(new_test_attributes)
            end
end

Modify app\\assets\\javascripts\\tests.coffee and app\\helpers\\application_helper exactly like it's specified in the railscast:

app\\assets\\javascripts\\tests.coffee:

jQuery ->
    $(document).on 'click', 'form .add_fields', (event) ->
        time = new Date().getTime()
        regexp = new RegExp($(this).data('id'), 'g')
        $(this).before($(this).data('fields').replace(regexp, time))
        event.preventDefault()

app\\helpers\\application_helper.rb:

def link_to_add_fields(name, f, association)
        new_object = f.object.send(association).klass.new
        id = new_object.object_id
        fields = f.fields_for(association, new_object, child_index: id) do |builder|
            render(association.to_s.singularize + "_fields", f: builder)
        end
        link_to(name, '#', class: "add_fields", data: {id: id, fields: fields.gsub("\n", "")})
    end

Above is the complete set of steps that worked for me and I can create and save multiple tests for a student in one go.