在 Rails 中动态创建模型的多个实例

Question

我有两个相关的模型“Test”和“Student”：

class Student< ActiveRecord::Base
   has_many :tests
end

class Test< ActiveRecord::Base
   belongs_to :Student
end

我要做的是为学生创建未知数量的测试，即从学生的 show.html.erb 中，用户可以创建多个测试。此外，一旦创建了一组测试，用户就可以像以前一样通过学生的 show.html.erb 再次添加任意数量的测试。

请注意，创建测试不是学生创建的一部分（就像在this railscast 中一样）。学生是单独创建的，然后可以通过 app/views/students/show.html.erb 上的按钮添加多个测试。

当单击添加测试的按钮时，我正在students_controller.rb 中调用自定义操作（下面的customAction1）。我能想到的是动态构建和附加，例如 10 个（开始）测试实例到学生的实例（在 students_controller.rb 的自定义操作中），呈现自定义视图（下面的 addtests.html.erb），然后允许用户在该视图中为这些测试实例输入各种输入字段，最后当单击创建按钮时，调用 student_controller.rb 中的另一个自定义操作（下面的 customAction2）来保存（仅非空的）测试实例。

这是正确的（阅读 Rails）方法吗？由于我是 Rails 新手，请更正执行上述操作的代码：

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

如果这确实是正确的方法，请告诉我如何编写 addtests.html.erb 视图。

Answer 1

您仍然可以通过学生将测试添加为更新学生而不是创建并使用cocoon gem 来帮助您处理嵌套表格，我正在考虑这样的事情

宝石文件

gem 'cocoon'

宝石链接：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

学生/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

此表单将提交到students#update 操作，test_attributes 仅作为参数

测试/_test_fields.html.haml

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

Answer 2

我最终观看了嵌套表单railscast 的修订版以解决问题。步骤如下：

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

修改 app\assets\javascripts\tests.coffee 和 app\helpers\application_helper 就像在 railscast 中指定的一样：

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

以上是对我有用的完整步骤集，我可以一次性为一名学生创建和保存多个测试。