Partner()预期，got String()

Question

我有一个课程模型，和类别有很多关系，我在我的表单上使用多个选择来获得一个对象数组，一个课程也可以有一个合作伙伴，用户可以从一个选择中选择这个，但是当我想要保存到数据库时，我调用params，然后我得到一个字符串而不是一个对象。不知道我怎么能解决这个问题

<%= form_for @course do |f| %>

<section class="new_course">
  <div class="row collapse">
    <div class="medium-5 small-centered column">     
      <%= f.label :course_title, :class=>"custom-prefix-class" %>
      <%= f.text_field :title, :autofocus => true, :class=>"custom-input-class" %>
    </div>
  </div>

  <div class="row collapse">
    <div class="medium-5 small-centered column">     
      <%= f.label :start_date, :class=>"custom-prefix-class" %>
      <%= f.text_field :start_date, :class=>"custom-input-class" %>
    </div>
  </div>

  <div class="row">
    <div class="medium-5  column with_chosen"> 
      <%= f.collection_select :categories,
      Category.all ,:id,:name,
      { include_blank: true},
      { class: 'chosen-select', :multiple=>true, :data => { :placeholder => ' ' }}
      %>
    </div>
  </div>
  <div class="row">
    <div class="medium-5  column"> 
      <%= f.collection_select :partner,
      Partner.all.collect, :id,:name ,
      { include_blank: true },
      { class: 'chosen-select', :multiple=>false, :data => { :placeholder => ' Brand Partner' }}
      %>
    </div>
  </div>

在我的控制器里

def create
  @course = Course.new(course_params)

  end
  if @course.save
    render :action=>'new'  
  end     
end

private
def course_params    
  params.require(:course).permit(:title, :start_date,:duration,:partner,:categories => [])
end

//rails服务器输出

Started POST "/courses" for 127.0.0.1 at 2014-02-07 16:45:28 +0200
Processing by CoursesController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"sKhAF2X6VOXTxZC9Pt51RFQfZSKdzXVWji6x4uwg+rI=", "course"=>{"title"=>"Marketing ", "start_date"=>"14-02-2014", "categories"=>["", "1", "2"], "partner"=>"1", "duration"=>"2-weeks"}, "commit"=>"Add new course"}
Completed 500 Internal Server Error in 3ms

ActiveRecord::AssociationTypeMismatch (Partner(#70274068591140) expected, got String(#70274066607160)):
  app/controllers/courses_controller.rb:24:in `create'

Answer 1

试试这个：-

似乎该合作伙伴是一个模型和课程has_one合作伙伴，因此您必须将合作伙伴类对象分配给合作伙伴类对象，而不是实际上将id指定为字符串，就像您在

  params[:course][:partner] 
  => "1"

现在是一个字符串，如果您尝试执行类似于@course.partner = '1‘的操作，它将引发一个类似于上面的错误，因为在左侧我们有parter关联，而右侧有一个字符串。

就这么做

def course_params    
  params.require(:course).permit(:title, :start_date,:duration,:partner,:categories => [])   
  if params[:course][:partner].present?
    params[:course][:partner] = Partner.find params[:course][:partner] 
  end
end