Why does my code create an extra object? - ruby-on-rails

Question

I want to create an object with random sequence generated through the follow method. But after clicking the "Generate" button, it creates 2 objects (1 with all attributes null and the other 1 with the value I entered). Can someone tell me where's the problem?
CONTROLLER :
class GeneratorsController < ApplicationController
before_action :set_generator, only: [:show, :edit, :update, :destroy]
after_action :random_generate, only: [:create, :new, :edit]
# GET /generators
# GET /generators.json
def index
#generators = Generator.all
end
# GET /generators/1
# GET /generators/1.json
def show
end
# GET /generators/new
def new
#generator = Generator.new
end
# GET /generators/1/edit
def edit
end
# POST /generators
# POST /generators.json
def create
#generator = Generator.new(generator_params)
respond_to do |format|
if #generator.save
format.html { redirect_to #generator, notice: 'Generator was successfully created.' }
format.json { render action: 'show', status: :created, location: #generator }
else
format.html { render action: 'new' }
format.json { render json: #generator.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /generators/1
# PATCH/PUT /generators/1.json
def update
respond_to do |format|
if #generator.update(generator_params)
format.html { redirect_to #generator, notice: 'Generator was successfully updated.' }
format.json { head :no_content }
else
format.html { render action: 'edit' }
format.json { render json: #generator.errors, status: :unprocessable_entity }
end
end
end
# DELETE /generators/1
# DELETE /generators/1.json
def destroy
#generator.destroy
respond_to do |format|
format.html { redirect_to generators_url }
format.json { head :no_content }
end
end
def random_generate
if #generator.choice == 'Randomly'
length = #generator.primer_length
chars = 'ATGC'
seq = ''
length.times { seq << chars[rand(chars.size)] }
#generator.random_primer_generated = seq
end
#generator.save!
end
private
# Use callbacks to share common setup or constraints between actions.
def set_generator
#generator = Generator.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def generator_params
params.require(:generator).permit(:primer_length, :choice, :random_primer_generated)
end
end
VIEW :
<%= form_for (#generator ) do |f| %>
<% if #generator.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(#generator.errors.count, "error") %> prohibited this generator from being saved:</h2>
<ul>
<% #generator.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="field">
<label>Primer Length</label><br>
<%= f.number_field :primer_length %>
</div>
<label>Selection :</label><br>
<label>Randomly</label>
<%= radio_button_tag(:choice, 'Randomly')%>
<%= button_to('Generate', random_generate_generator_path(#generator))%>
<% end %>

Answer 1

You have an after_action callback which triggers the random_generate action every time you display the new view. That's where your empty object comes from. You shouldn't need this after_action callback on new.