Ruby on Rails - I can't send a form - 400 Bad Request

Question

I'm trying send a form in Ruby on Rails, but when try send I get the following error:

Started POST "/newsletters" for 127.0.0.1 at 2018-05-02 14:26:33 -0300
Processing by NewslettersController#create as JS
Parameters: {"utf8"=>"✓"}
[1m[35m (0.2ms)[0m  BEGIN
[1m[36m (0.4ms)[0m  [1mROLLBACK[0m
Rendered text template (0.0ms)
Completed 400 Bad Request in 14ms (Views: 0.7ms | ActiveRecord: 0.6ms)

The form has just one field (email) and I already validate it in my model. What's going on? Why 400 Bad Request? Anyone con help me?

newsletter_mailer.rb

class NewsletterMailer < ActionMailer::Base
  default from: "no-reply@facens.br"

  def create(contact)
    @contact = contact
    mail(to: "felipe.marcon@atua.ag", subject: "Contato Através do Site")
  end
end

newsletters_controller.rb

class NewslettersController < ApplicationController
  def create
    @newsletter = Newsletter.new(params[:newsletters])
    if @newsletter.save
      NewsletterMailer.delay_for(1.seconds, retry: true).create(@newsletter)
      render nothing: true, status: 200
    else
      render nothing: true, status: 400
    end
  end
end

form.html.erb

<%= form_for(Newsletter.new, remote: true, html: { multipart: true }, html: {class:"fc_liga__footer--form clearfix"}) do |f| %>
  <div class="input_group">
    <input type="text" id="contact[email]" placeholder="Digite o seu e-mail">
    <button type="submit" class="btn btn_orange"><%= svg "send_newsletter" %></button>
  </div>
<% end %>

Answer 1

Your parameters don't include :newsletters , see?

Parameters: {"utf8"=>"✓"}

So, @newsletter.save is false and you get a 400 error, just as you specified:

class NewslettersController < ApplicationController
  def create
    @newsletter = Newsletter.new(params[:newsletters])
    if @newsletter.save
      NewsletterMailer.delay_for(1.seconds, retry: true).create(@newsletter)
      render nothing: true, status: 200
    else
      render nothing: true, status: 400
    end
  end
end

You don't have params[:newsletters] because your form is malformed:

<%= form_for(Newsletter.new, remote: true, html: { multipart: true }, html: {class:"fc_liga__footer--form clearfix"}) do |f| %>
  <div class="input_group">
    <input type="text" id="contact[email]" placeholder="Digite o seu e-mail">
    <button type="submit" class="btn btn_orange"><%= svg "send_newsletter" %></button>
  </div>
<% end %>

You shouldn't manually create the input, you should use an input helper instead.