Rails中的Ajax POST请求错误

Question

I'm trying to implement Ajax for the first time in simple Rails app, helped mainly by this tutorial:

Integrating Ajax and Rails

My app has a particular show view where I want to display a leaderboard that renders a list of users and their record plus a form where new users/records can be created.

I'd like to achieve this via Ajax but every time I try to submit an Ajax request I get a 500 error pointing to the below JQuery line and throwing a 'Failed to load resource' message.

xhr.send( ( options.hasContent && options.data ) || null );  

I've tried to change a few things without success, including using remote:true in the form and making the Ajax request directly with JQuery. Could you point me to the potential problem here? Below the relevant code:

leaderboards_Controller Show action renders the relevant leaderboard

  def show
   @leaderboard = Leaderboard.find(params[:id])
   @leaders = @leaderboard.leaders
   @leader = Leader.new(persisted_time: @persisted_time)
  end

leaderboards/show.html.erb

  <%= simple_form_for([@leaderboard, @leader], html: { class: 'form-inline', id:'leader-form' }) do |f| %>
    <%= f.error_notification %>
    <div class="form-inputs">
      <%= f.input :name, :label => false, :placeholder => "Your name here", :required => true, :autofocus => true %>
      <%= f.input :record_time, :label => "Your record", input_html: {readonly: ''} %>
      <%= f.button :submit %>
    </div>
  <% end %>

  <ul>
  <% @leaders.each do |leader| %>
    <li>
      <%= leader.name %> |
      <strong>record: </strong><%= leader.record_time %> <br />
    </li>
  <% end %>
  </ul>

leaders_Controller I'm intending to send the Ajax request to the create action in this controller when submitting the form above

class LeadersController < ApplicationController
  before_action :set_leader, only: [:show, :edit, :update, :destroy]
  before_action :set_leaderboard, only: [:create, :new]

  def index
    @leaders = Leader.all
  end

  def show
  end

  def new
  end

  def edit
  end

  def create
     @leaderboard = Leaderboard.find(params[:leaderboard_id])
     @leader = Leader.new(leader_params)
     @leader.leaderboard_id = @leaderboard.id
     respond_to do |format|
        if @leader.save
          format.json { render json: @leader, status: :created}
        else
          format.json { render json: @leader.errors, status: :unprocessable_entity }
        end
     end
  end

  def update
    @leader.update_attributes(leader_params)
  end

  def destroy
    @leader.destroy
  end

  private
    def set_leader
      @leader = Leader.find(params[:id])
    end

    def set_leaderboard
      @leaderboard = Leaderboard.find(params[:leaderboard_id])
    end

    def leader_params
      params.require(:leader).permit(:name, :record_time, :leaderboard_id)
    end
end

assets/javascripts/leaders.js the JS file where I'm doing the Ajax request

$(function(){
  $("form").submit(function(event){
  event.preventDefault();

  var action = $(this).attr('action');
  var method = $(this).attr('method');

  var name = $(this).find('#leader_name').val();
  var record_time = $(this).find('#leader_record_time').val();

  $.ajax({
    method: method,
    url: action,
    data: { name: name, record_time: record_time }
  });

  });
});

and the routes

  resources :leaderboards, shallow: true do
   resources :leaders
  end

I'm clearly not getting something about Ajax. I'd appreciate if you point me to the right direction.

here's the output I get in the console after submiting the form

jquery.self-bd7ddd3….js?body=1:10255 POST http://localhost:3000/leaderboards/1/leaders 500 (Internal Server Error)

this leads to this line in the JQuery script:

xhr.send( ( options.hasContent && options.data ) || null );

and produces:

Failed to load resource: the server responded with a status of 500 (Internal Server Error)

and server log

         Started POST "/leaderboards/1/leaders" for ::1 at 2016-11-28 21:42:24 +1100
Processing by LeadersController#create as JS
  Parameters: {"utf8"=>"✓", "leader"=>{"name"=>"9089sdas8dds", "persisted_time"=>"5"}, "commit"=>"S", "leaderboard_id"=>"1"}
  Leaderboard Load (0.5ms)  SELECT  "leaderboards".* FROM "leaderboards" WHERE "leaderboards"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
  CACHE (0.0ms)  SELECT  "leaderboards".* FROM "leaderboards" WHERE "leaderboards"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
   (0.2ms)  BEGIN
  Leaderboard Load (0.4ms)  SELECT  "leaderboards".* FROM "leaderboards" WHERE "leaderboards"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
  SQL (2.6ms)  INSERT INTO "leaders" ("name", "persisted_time", "leaderboard_id", "created_at", "updated_at") VALUES ($1, $2, $3, $4, $5) RETURNING "id"  [["name", "9089sdas8dds"], ["persisted_time", "5"], ["leaderboard_id", 1], ["created_at", 2016-11-28 10:42:24 UTC], ["updated_at", 2016-11-28 10:42:24 UTC]]
   (2.2ms)  COMMIT
Completed 201 Created in 15ms (Views: 0.8ms | ActiveRecord: 5.9ms)


Started POST "/leaderboards/1/leaders" for ::1 at 2016-11-28 21:42:27 +1100
Processing by LeadersController#create as JS
  Parameters: {"utf8"=>"✓", "leader"=>{"name"=>"9089sdas8dds", "persisted_time"=>"5"}, "commit"=>"S", "leaderboard_id"=>"1"}
  Leaderboard Load (0.5ms)  SELECT  "leaderboards".* FROM "leaderboards" WHERE "leaderboards"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
  CACHE (0.0ms)  SELECT  "leaderboards".* FROM "leaderboards" WHERE "leaderboards"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
   (0.7ms)  BEGIN
  Leaderboard Load (0.5ms)  SELECT  "leaderboards".* FROM "leaderboards" WHERE "leaderboards"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
  SQL (1.9ms)  INSERT INTO "leaders" ("name", "persisted_time", "leaderboard_id", "created_at", "updated_at") VALUES ($1, $2, $3, $4, $5) RETURNING "id"  [["name", "9089sdas8dds"], ["persisted_time", "5"], ["leaderboard_id", 1], ["created_at", 2016-11-28 10:42:27 UTC], ["updated_at", 2016-11-28 10:42:27 UTC]]
   (0.5ms)  COMMIT
Completed 201 Created in 14ms (Views: 1.0ms | ActiveRecord: 4.2ms)


Started POST "/leaderboards/1/leaders" for ::1 at 2016-11-28 21:42:29 +1100
Processing by LeadersController#create as JS
  Parameters: {"utf8"=>"✓", "leader"=>{"name"=>"9089sdas8dds", "persisted_time"=>"5"}, "commit"=>"S", "leaderboard_id"=>"1"}
  Leaderboard Load (0.6ms)  SELECT  "leaderboards".* FROM "leaderboards" WHERE "leaderboards"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
  CACHE (0.0ms)  SELECT  "leaderboards".* FROM "leaderboards" WHERE "leaderboards"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
   (0.2ms)  BEGIN
  Leaderboard Load (0.6ms)  SELECT  "leaderboards".* FROM "leaderboards" WHERE "leaderboards"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
  SQL (2.3ms)  INSERT INTO "leaders" ("name", "persisted_time", "leaderboard_id", "created_at", "updated_at") VALUES ($1, $2, $3, $4, $5) RETURNING "id"  [["name", "9089sdas8dds"], ["persisted_time", "5"], ["leaderboard_id", 1], ["created_at", 2016-11-28 10:42:29 UTC], ["updated_at", 2016-11-28 10:42:29 UTC]]
   (2.3ms)  COMMIT
Completed 201 Created in 14ms (Views: 0.7ms | ActiveRecord: 6.0ms)

Answer 1

try adding

respond_to(:js)

at the end of your create method.

And yes, please just use remote: true

Answer 2

Please update your code as below.

show.html.erb

<%= simple_form_for([@leaderboard, @leader],remote: true, html: { class: 'form-inline', id:'leader-form' }) do |f| %>
    <%= f.error_notification %>
    <div class="form-inputs">
      <%= f.input :name, :label => false, :placeholder => "Your name here", :required => true, :autofocus => true %>
      <%= f.input :record_time, :label => "Your record", input_html: {readonly: ''} %>
      <%= f.button :submit %>
    </div>
  <% end %>

  <ul>
  <% @leaders.each do |leader| %>
    <li>
      <%= leader.name %> |
      <strong>record: </strong><%= leader.record_time %> <br />
    </li>
  <% end %>
  </ul>

leaders_Controller

def create
   @leaderboard = Leaderboard.find(params[:leaderboard_id])
   @leader = Leader.new(leader_params)
   @leader.leaderboard_id = @leaderboard.id
   respond_to do |format|
    if @leader.save
      format.json { render json: @leader, status: :created}
    else
      format.json { render json: @leader.errors, status: :unprocessable_entity }
    end 
   end 
  end

assets/javascripts/leaders.js

$(function(){    
return $("#your-form-id").on("ajax:success", function(e, data, status, xhr) {
            e.preventDefault();
            // success code 
        }).on("ajax:error", function(e, xhr, status, error) {
            // error code
        });
});