undefined method `gsub' for nil:NilClass or how to use gsub method in rails

Question

I want to generate an Employee_ID with serially, I have fixed a initial employee id in database table. the format is "E36162000", I am taking last employee id from table then extract only integer value then add one, this will be next employee id .

But in this gsub() method is not working, gsub method extract integer is perfectly, link Next Employee_id = E36162001

But when am i submit then error comes. I am sending code and screen sort please help me

_employee_details.html.erb - this is my view

<div class="modal-body">
    <h2 class="text-center">Add <span>Employee Details</span></h2>
    <div class="post-new-job head-border">
      <div class="alert alert-success" role="alert" id='success-job' style='display:none;'>Employee Details is successfully added.</div>
        <div class="form-body">             
            <%= form_for(:employee_details, :url => {:controller => 'hr', :action => 'create'}) do |f| %>                   
                <div class="col-md-12">
                <!--auto generate emp id-->
                <% @last_emp_id = EmployeeDetail.select("employee_id").last %>
                <% emp_id = @last_emp_id.employee_id  %>
                <% emp_id_sub = emp_id.gsub(/[^\d]/, '') %>
                <% auto_generate_id = 'E'.to_s + (emp_id_sub.to_i + 1).to_s %>
                <h1> Employee ID : <%= auto_generate_id %> </h1>


                <div class="mydata">
                 <%= f.hidden_field :offer_letter_id, { class: 'form-control', id: 'recipient-name' } %>
                </div>

                 <div class="form-group">
                    <label class="control-label">Employee ID</label>
                    <div class="input-group"> <span class="input-group-addon"> <i class="fa fa-user"></i> </span>
                      <%= f.text_field :employee_id, { :value => auto_generate_id, :disabled=>true , :required => true, placeholder: 'E12345678', class: 'form-control' } %>
                    </div>
                  </div>

                  <div class="form-group">
                    <label class="control-label">Bank Account</label>
                    <div class="input-group"> <span class="input-group-addon"> <i class="fa fa-university"></i> </span>
                      <%= f.text_field :bank_ac, {placeholder: '06464060852634865', class: 'form-control' } %>
                    </div>
                  </div>

                  <div class="form-group">
                    <label class="control-label">Bank IFSC Code</label>
                    <div class="input-group"> <span class="input-group-addon"> <i class="fa fa-code"></i> </span>
                      <%= f.text_field :bank_ifsc, {placeholder: 'SBI012356', class: 'form-control' } %>
                    </div>
                  </div>

                  <div class="form-group">
                    <label class="control-label">End of Date</label>
                    <div class="input-group"> <span class="input-group-addon"> <i class="fa fa-calendar"></i> </span>
                      <%= f.text_field :work_end_date, {  placeholder: 'MM/DD/YYYY', id: 'datepicker', class:"datepicker_style" } %>
                    </div>
                  </div>

                  <div class="form-group">
                    <label class="control-label">Gender</label>
                    <div class="input-group"> <span class="input-group-addon"> <i class="fa fa-male fa-female"></i> </span>
                      <%= f.select :gender, ['Male', 'Female'], { }, class: "form-control" %>
                    </div> 
                  </div>

                  <div class="form-group">
                    <label class="control-label">Spouse Name</label>
                    <div class="input-group"> <span class="input-group-addon"> <i class="fa fa-user"></i> </span>
                      <%= f.text_field :spouse_name, { placeholder: 'Father/Mother/Wife name', class: "form-control" } %>
                    </div>
                  </div> <br>

                  <div class="form-group">
                    <a><%= f.submit "Add Employee Details", :class => "btn btn-primary" %></a> 
                  </div>
                </div>
                <div class="col-md-2"></div>                
            <%- end -%>
        </div>      
    </div>
   </div>

employee_details.rb - this is my model

class EmployeeDetail < ActiveRecord::Base
   belongs_to :user
   validates :offer_letter_id, presence: true 
end

hr_controller.rb - this is my controler

class HrController < ApplicationController
def new
    @employees = EmployeeDetail.new
end

# edit employee information
def edit
    @employees = EmployeeDetail.find(params[:id])
end

def create
    @employees = EmployeeDetail.new(employee_params)
    if @employees.save
        redirect_to :action => 'internal_employee_page'
    else
        redirect_to :action => 'internal_employee_page'
    end
end

def show
    @employees = EmployeeDetail.find(params[:id])
end

def update
    @employees = EmployeeDetail.find(params[:id])

    if @employees.update(employee_params)
        redirect_to :action => 'internal_employee_page'
    else
        redirect_to :action => 'internal_employee_page'
    end
end

private

    def employee_params
         params.require(:employee_details).permit(:offer_letter_id, :employee_id, :bank_ac, :bank_ifsc, :spouse_name, :gender, :work_end_date)
    end     
 end

my layout View

**Error in this line **

<% emp_id_sub = emp_id.gsub(/[^\\d]/, '') %>

error is

When am i Click on submit button then error is generate but data is save in employee_details table except Employee_Id

Answer 1

You might not have the emp_id . Try changing the code to,

<% @last_emp_id = EmployeeDetail.select("employee_id").last %>
<% emp_id = @last_emp_id.employee_id  %>
<% emp_id_sub = emp_id.present? ? emp_id.gsub(/[^\d]/, '') : ''%>
<% auto_generate_id = emp_id_sub.length > 0 ? ? ('E'.to_s + (emp_id_sub.to_i + 1).to_s) : "" %>
<h1> Employee ID : <%= auto_generate_id %> </h1>

checking the presence of emp_id and then emp_id_sub

Update: Added a sample query using select as per comment of @mudasobwa

2.3.1 :015 > @user = User.select("email").last
  User Load (0.5ms)  SELECT  `users`.`email` FROM `users`  ORDER BY `users`.`id` DESC LIMIT 1

 => #<User id: nil, email: "test@ead.com"> 

2.3.1 :016 > email = @user.email
 => "test@ead.com" 

Answer 2

We can create also a method in the model and we can call before_save, whenever create a new employeee details then before save it will be execute and store employee id into database

class EmployeeDetail < ActiveRecord::Base
belongs_to :user
validates :offer_letter_id, presence: true
# auto generate employee id
before_save :Auto_generate_emp_id

def Auto_generate_emp_id
    @last_emp_id = EmployeeDetail.order("employee_id").last 
    emp_id = @last_emp_id.employee_id
    emp_id_sub = emp_id.gsub(/[^\d]/, '')
    auto_generate_id = 'E'.to_s + (emp_id_sub.to_i + 1).to_s 
    self.employee_id = auto_generate_id
end

end