So I have locker model which is just a basic scaffold
def change
create_table :lockers do |t|
t.references :user
t.integer :lockerNo
t.string :wing
t.string :sttatus
t.string :comment
t.timestamps
end
end
end
and also a user model which is just basic devise.
I want users to be able to select a locker they want,
So I want to list all the lockers and then users click on Select button and then the locker gets assigned to the user i.e the locker_id updates to the current user
This is my controller
before_action :set_locker, only: [:show, :edit, :update, :destroy]
# GET /lockers
# GET /lockers.json
def index
#lockers = Locker.all
end
# POST /lockers
# POST /lockers.json
def create
#locker = Locker.new(locker_params)
respond_to do |format|
if #locker.save
format.html { redirect_to #locker, notice: 'Locker was successfully created.' }
format.json { render :show, status: :created, location: #locker }
else
format.html { render :new }
format.json { render json: #locker.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /lockers/1
# PATCH/PUT /lockers/1.json
def update
respond_to do |format|
if #locker.update(locker_params)
format.html { redirect_to #locker, notice: 'Locker was successfully updated.' }
format.json { render :show, status: :ok, location: #locker }
else
format.html { render :edit }
format.json { render json: #locker.errors, status: :unprocessable_entity }
end
end
end
def assign_locker
if #locker.sttatus = Available
#locker = Locker.find(params[:id])
#locker.user_id = current_user.id
#locker.save
end
redirect_to root_path
end
private
def set_locker
#locker = Locker.find(params[:id])
end
def locker_params
params.require(:locker).permit(:user_id, :lockerNo, :wing, :sttatus, :comment)
end
end
Make a controller method for updating the locker with the current user.
Put /lockers/[locker_id]
def update
locker = Locker.findById(params[:locker_id])
locker.user = current_user
if locker.save
head 200
else
head 422
end
end
That's really ugly code that makes a few assumptions... but is it not what you're trying to do?
Related
I get for what is this error, but I can't see a mistake in my code.
A controller is plural, a model is singular and the table name is plural.
Error on visiting index:
NameError at /admin/custom_communities uninitialized constant
Admin::CustomCommunitiesController::CustomCommunity
Generated controller: (file: controllers/admin/custom_communities_controller.rb)
# frozen_string_literal: true
class Admin::CustomCommunitiesController < Admin::BaseController
before_action :set_custom_community, only: [:show, :edit, :update, :destroy]
def index
#custom_communities = CustomCommunity.page(params[:page])
end
def show; end
def new
#custom_community = CustomCommunity.new
end
def edit; end
def create
#custom_community = CustomCommunity.new(custom_community_params)
respond_to do |format|
if #custom_community.save
format.html { redirect_to #custom_community, notice: "Custom community was successfully created." }
format.json { render :show, status: :created, location: #custom_community }
else
format.html { render :new }
format.json { render json: #custom_community.errors, status: :unprocessable_entity }
end
end
end
def update
respond_to do |format|
if #custom_community.update(custom_community_params)
format.html { redirect_to #custom_community, notice: "Custom community was successfully updated." }
format.json { render :show, status: :ok, location: #custom_community }
else
format.html { render :edit }
format.json { render json: #custom_community.errors, status: :unprocessable_entity }
end
end
end
def destroy
#custom_community.destroy
respond_to do |format|
format.html { redirect_to admin_custom_communities_url, notice: "Custom community was successfully destroyed." }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_custom_community
#custom_community = CustomCommunity.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def custom_community_params
params.require(:custom_community).permit(:name, :description, :picture, :should_delete_picture)
end
end
Model: (file: models/custom_community.rb)
# frozen_string_literal: true
class CustomCommunity < ApplicationRecord
end
Migration:
class CreateCustomCommunities < ActiveRecord::Migration[5.2]
def change
create_table :custom_communities do |t|
t.string :name
t.text :description
t.timestamps
end
end
end
Routes:
in admin routes:
resources :custom_communities
I'm sure someone else can explain why, but there are times rails will think that the following class in the index method:
class Admin::CustomCommunitiesController < Admin::BaseController
def index
CustomCommunity.all
end
end
Is referencing a class defined within the Admin::CustomCommunitiesController, i.e. it thinks you're trying to call Admin::CustomCommunitiesController::CustomCommunity.all. To 'unnamespace' the class, try:
# frozen_string_literal: true
class Admin::CustomCommunitiesController < Admin::BaseController
before_action :set_custom_community, only: [:show, :edit, :update, :destroy]
def index
#custom_communities = ::CustomCommunity.page(params[:page])
end
def show; end
def new
#custom_community = ::CustomCommunity.new
end
def edit; end
def create
#custom_community = ::CustomCommunity.new(custom_community_params)
respond_to do |format|
if #custom_community.save
format.html { redirect_to #custom_community, notice: "Custom community was successfully created." }
format.json { render :show, status: :created, location: #custom_community }
else
format.html { render :new }
format.json { render json: #custom_community.errors, status: :unprocessable_entity }
end
end
end
def update
respond_to do |format|
if #custom_community.update(custom_community_params)
format.html { redirect_to #custom_community, notice: "Custom community was successfully updated." }
format.json { render :show, status: :ok, location: #custom_community }
else
format.html { render :edit }
format.json { render json: #custom_community.errors, status: :unprocessable_entity }
end
end
end
def destroy
#custom_community.destroy
respond_to do |format|
format.html { redirect_to admin_custom_communities_url, notice: "Custom community was successfully destroyed." }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_custom_community
#custom_community = ::CustomCommunity.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def custom_community_params
params.require(:custom_community).permit(:name, :description, :picture, :should_delete_picture)
end
end
I think that's all of them. Basically switch every CustomCommunity class call to ::CustomCommunity to unnamespace it.
i have ProjectSite model and ManagerRemark model related to many to one association. my MangerRemark model has boolean value true and false i want to access that boolean value to other controller view. please help. here is my code.i want to print decision boolean value next to each project site index list how can i do that? in other controller name new_manager_controller view
project_sites_controller.rb
class ProjectSitesController < ApplicationController
before_action :authenticate_user!
before_action :is_project_site?, except: [:show]
before_action :set_project_site, only: [:show, :edit, :update, :destroy]
# GET /project_sites
# GET /project_sites.json
def index
#project_sites = ProjectSite.all.order("created_at DESC")
end
# GET /project_sites/1
# GET /project_sites/1.json
def show
#manager_remark = ManagerRemark.new
#manager_remark.project_site_id = #project_site.id
end
# GET /project_sites/new
def new
#project_site = ProjectSite.new
end
# GET /project_sites/1/edit
def edit
end
# POST /project_sites
# POST /project_sites.json
def create
#project_site = ProjectSite.new(project_site_params)
respond_to do |format|
if #project_site.save
format.html { redirect_to #project_site, notice: 'Project site was successfully created.' }
format.json { render :show, status: :created, location: #project_site }
else
format.html { render :new }
format.json { render json: #project_site.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /project_sites/1
# PATCH/PUT /project_sites/1.json
def update
respond_to do |format|
if #project_site.update(project_site_params)
format.html { redirect_to #project_site, notice: 'Project site was successfully updated.' }
format.json { render :show, status: :ok, location: #project_site }
else
format.html { render :edit }
format.json { render json: #project_site.errors, status: :unprocessable_entity }
end
end
end
# DELETE /project_sites/1
# DELETE /project_sites/1.json
def destroy
#project_site.destroy
respond_to do |format|
format.html { redirect_to project_sites_url, notice: 'Project site was successfully destroyed.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_project_site
#project_site = ProjectSite.find(params[:id])
end
# Never trust parameters frmanager_level_twoom the scary internet, only allow the white list through.
def project_site_params
params.require(:project_site).permit(:name, :date, :file)
end
def is_project_site?
redirect_to root_path unless (current_user.role=='project_site')
end
end
This is how my manage remark controller looks.
Manager_Remarks_controller.rb
class ManagerRemarksController < ApplicationController
def create
#manager_remark = ManagerRemark.new(remark_params)
#manager_remark.project_site_id = params[:project_site_id]
#manager_remark.save
redirect_to project_site_path(#manager_remark.project_site)
end
def remark_params
params.require(:manager_remark).permit(:name, :remark, :decision)
end
end
Running Rails:
Rails 4.2.5
ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-linux]
I'm trying to return a value from one model (eds) within a view of another model (clients).
I believe I I'm very close to a solution. However, I'm at a road block. I'm want return the name of the school (eds) in the client view.
As of now, I'm defining this in my client controller:
def index
#eds_school = Ed.name
end
I thought that Ed.name should work but it doesn't.
Then I'm calling the statement in the view:
<tb><%= #eds_school %></td>
I think my issue is within the client controller.
Here is the db schema:
create_table "eds", force: :cascade do |t|
t.string "name"
t.string "grade"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.text "school"
t.text "JtText"
end
Eds Controller:
class EdsController < ApplicationController
before_action :set_ed, only: [:show, :edit, :update, :destroy]
# GET /eds
# GET /eds.json
def index
#eds = Ed.all
end
# GET /eds/1
# GET /eds/1.json
def show
end
# GET /eds/new
def new
#ed = Ed.new
end
# GET /eds/1/edit
def edit
end
# POST /eds
# POST /eds.json
def create
#ed = Ed.new(ed_params)
respond_to do |format|
if #ed.save
format.html { redirect_to #ed, notice: 'Ed was successfully created.' }
format.json { render :show, status: :created, location: #ed }
else
format.html { render :new }
format.json { render json: #ed.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /eds/1
# PATCH/PUT /eds/1.json
def update
respond_to do |format|
if #ed.update(ed_params)
format.html { redirect_to #ed, notice: 'Ed was successfully updated.' }
format.json { render :show, status: :ok, location: #ed }
else
format.html { render :edit }
format.json { render json: #ed.errors, status: :unprocessable_entity }
end
end
end
# DELETE /eds/1
# DELETE /eds/1.json
def destroy
#ed.destroy
respond_to do |format|
format.html { redirect_to eds_url, notice: 'Ed was successfully destroyed.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_ed
#ed = Ed.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def ed_params
params.require(:ed).permit(:name)
end
end
Client Controller:
class ClientsController < ApplicationController
before_action :authenticate_user!
before_action :set_client, only: [:show, :edit, :update, :destroy]
# GET /clients
# GET /clients.json
def index
#clients = Client.all.uniq.order("created_at DESC")
#clients_count = Client.uniq.count
#eds_school = Ed.name
end
# GET /clients/1
# GET /clients/1.json
def show
##notes = Note.all.uniq.order("created_at DESC")
#notes = Note.where(client_id: #client.id) #Where a note belong to the current user
end
# GET /clients/new
def new
#client = Client.new
end
# GET /clients/1/edit
def edit
end
# POST /clients
# POST /clients.json
def create
#client = Client.new(client_params)
respond_to do |format|
if #client.save
format.html { redirect_to #client, notice: 'Client was successfully created.' }
format.json { render :show, status: :created, location: #client }
else
format.html { render :new }
format.json { render json: #client.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /clients/1
# PATCH/PUT /clients/1.json
def update
#if params[:remove_image]
##client.remove_image!
#client.save
#end
respond_to do |format|
if #client.update(client_params)
format.html { redirect_to #client, notice: 'Client was successfully updated.' }
format.json { render :show, status: :ok, location: #client }
else
format.html { render :edit }
format.json { render json: #client.errors, status: :unprocessable_entity }
end
end
end
# DELETE /clients/1
# DELETE /clients/1.json
def destroy
#client.destroy
respond_to do |format|
format.html { redirect_to clients_url, notice: 'Client was successfully destroyed.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_client
#client = Client.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def client_params
params.require(:client).permit(:firstName, :lastName,:dob, :name, :gender_id, :RefbText, :JtText, :text_rs, :msub, :text_id, :ged_id, :mj_id, :od_id, :otc_id, :cigarette_id, :alcohol_id, :grad, :remove_image, :rh_options, :insurance_id, :state_id, :ed_id, :wk_id, :grade_id, :rsource_id, :image, :race_id, :employment_id, :comments, :clientemail, :phone, :truma_id, :college_id, :enrolled, :address, :city, :state, :zipcode, rhealth_ids:[], mhealth_ids:[], cparent_ids:[], preg_ids:[], referral_ids:[], refa_ids:[], refb_ids:[])
#params.require(:client).permit(:name, mhealth_ids:[])
end
end
Code Sample of Client Model:
class Client < ActiveRecord::Base
belongs_to :ed
end
Code Sample of Client DB Schema:
create_table "clients", force: :cascade do |t|
t.integer "ed_id"
end
Ed Controller:
class Ed < ActiveRecord::Base
has_many :clients
end
Its not completely clear what you're trying to achieve. Your code isnt working bcause name is an attribute and therefore a method on an instance of the class Eds. Look up the difference between class methods and instance methods. You need to find a particular instance of Eds and then call the name method on it e.g.
eds_school = Eds.find(1).name
where 1 is the database record in the eds table with an id of 1.
Because a client belongs to an Eds, you can access the eds name through a client instance. To display the eds.name for each client, you will need to loop through the clients variable. In the view
<% #clients.each do |client| %>
<%= client.eds.name %>
<% end %>
ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-linux],
Rails 4.2.5
I have two projects. from 1st project i am getting data into second project through api.
User model in 1st project:
class User < ActiveRecord::Base
has_many :cars
end
Car model in 1st project:
class Car < ActiveRecord::Base
belongs_to :user
end
Car model(remote) in 2nd project:
class Car < ActiveResource::Base
self.site = 'https://myeasyb-vssram.c9users.io'
self.format = :json
end
Gpstablecontroller(2nd project):
class GpstablesController < ApplicationController
before_action :set_gpstable, only: [:show, :edit, :update, :destroy]
# GET /gpstables
# GET /gpstables.json
def index
#gpstables = Gpstable.all
end
# GET /gpstables/1
# GET /gpstables/1.json
def show
end
# GET /gpstables/new
def new
#gpstable = Gpstable.new
#gpstables = Gpstable.all
end
# GET /gpstables/1/edit
def edit
#gpstables = Gpstable.all
end
# POST /gpstables
# POST /gpstables.json
def create
#cars = Car.all
#gpstable = Gpstable.new(gpstable_params)
#cars.each do |car|
if #gpstable.car_id == car.id
#car = car
end
end
#car.update_attribute(:gpss, #gpstable.device_id)
respond_to do |format|
if #gpstable.save
format.html { redirect_to gpstables_url, notice: 'Gpstable was successfully created.' }
format.json { render :show, status: :created, location: #gpstable }
else
format.html { render :new }
format.json { render json: #gpstable.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /gpstables/1
# PATCH/PUT /gpstables/1.json
def update
respond_to do |format|
if #gpstable.update(gpstable_params)
Car.all.each do |car|
if #gpstable.car_id == car.id.to_json
#car = car
end
if #gpstable.device_id == car.gpss
car.gpss = 0
car.save!
end
end
#car.gpss = #gpstable.device_id
#car.save!
format.html { redirect_to #gpstable, notice: 'Gpstable was successfully updated.' }
format.json { render :show, status: :ok, location: #gpstable }
else
format.html { render :edit }
format.json { render json: #gpstable.errors, status: :unprocessable_entity }
end
end
end
# DELETE /gpstables/1
# DELETE /gpstables/1.json
def destroy
#cars.each do |car|
if #gpstable.device_id == car.gpss
car.gpss = 0
car.user_id = #gpstable.user_id
car.save
end
end
#gpstable.destroy
respond_to do |format|
format.html { redirect_to gpstables_url, notice: 'Gpstable was successfully destroyed.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_gpstable
#gpstable = Gpstable.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def gpstable_params
params.require(:gpstable).permit(:device_id, :car_id, :user_id)
end
end
when creating gpstable record i want to update Gpss attribute of car model(remote, calling through api).
it is updating gpss attribute.But it is changing all foriegnkeys including user_id attribute of car model to null.
using devise for users in 1st project.
The problem is i am giving user_id to current user_id in car_params. so i was unable to edit this through resource model. so i changed this to create action.
In my first app i have car controller:
def car_params
params.require(:car).permit(:name, :model, :colour, :ac, :gpss, :wifi, :luggage, :cfare, :card, :crfare, :no, :nos, :user_id, {carpicss: []} ).**merge(user: :current_user)**
end
i removed .merge(user: :current_user) from above code.
and added this in create action
def create
#car = Car.new(car_params)
#car.card=" #{#car.name} : #{#car.no}"
#car.user_id=current_user.id #added here to save current user_id
respond_to do |format|
if #car.save
format.html { redirect_to cars_path, notice: 'Car was successfully created.' }
format.json { render :show, status: :created, location: cars_path }
else
format.html { render :new }
format.json { render json: #car.errors, status: :unprocessable_entity }
end
#car.reload
end
end
I am getting NoMethodError in SitesController#index undefined method `name' for nil:NilClass in my Salesman index view and cannot find the culprit.
I have a simple rails app with the following tables: Customer, Salesman and Invoice.
In the index view for the customer table I have the following call:
<% #customers.each do |customer| %>
<%= customer.name %></td>
<%= customer.address %>
<%= customer.salesman.name %>
<% end %>
This is the call that results in the undefined method ´name´ listed above. I made sure the salesman table has a salesman_id foreign key in the customer table. Also, I made the respective association in the models:
class Customer < ActiveRecord::Base
belongs_to :salesman
has_many :invoices
end
class Salesman < ActiveRecord::Base
has_many :customers
end
I tested the customer.salesman.name call in the console and it works flawlessly. The show view for the customer has an exact call like this one and it also works. The only way I can make the customer index pass is by replacing customer.salesman.name to customer.salesman_id returning only the id.
Thank you for your time here.
***schema.rb***
ActiveRecord::Schema.define(version: 20150325172212) do
create_table "customers", force: :cascade do |t|
t.string "name"
t.string "address"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.integer "salesman_id"
end
create_table "invoices", force: :cascade do |t|
t.datetime "date"
t.string "fid"
t.integer "salesman_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.string "address"
end
create_table "salesmen", force: :cascade do |t|
t.datetime "name"
t.string "address""
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
***controllers***
**customer**
Class CustomersController < ApplicationController
before_action :set_customer, only: [:show, :edit, :update, :destroy]
# GET /customers
# GET /customers.json
def index
#customers = Customer.all
end
# GET /customers/1
# GET /customers/1.json
def show
end
# GET /customers/new
def new
#customer = Customer.new
end
# GET /customers/1/edit
def edit
end
# POST /customers
# POST /customers.json
def create
#customer = Customer.new(customer_params)
respond_to do |format|
if #customer.save
format.html { redirect_to #customer, notice: 'Customer was successfully created.' }
format.json { render :show, status: :created, location: #customer }
else
format.html { render :new }
format.json { render json: #customer.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /customers/1
# PATCH/PUT /customers/1.json
def update
respond_to do |format|
if #customer.update(customer_params)
format.html { redirect_to #customer, notice: 'Customer was successfully updated.' }
format.json { render :show, status: :ok, location: #customer }
else
format.html { render :edit }
format.json { render json: #customer.errors, status: :unprocessable_entity }
end
end
end
# DELETE /customers/1
# DELETE /customers/1.json
def destroy
#customer.destroy
respond_to do |format|
format.html { redirect_to customers_url, notice: 'Customer was successfully destroyed.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_cliente
#cliente = Cliente.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def customer_params
params.require(:customer).permit(:name, :address, :salesman_id)
end
end
***salesman***
class SalesmenController < ApplicationController
before_action :set_salesman, only: [:show, :edit, :update, :destroy]
# GET /salesmans
# GET /salesmans.json
def index
#salesmen = Salesman.all
end
# GET /salesmans/1
# GET /salesmans/1.json
def show
end
# GET /salesmans/new
def new
#salesman = Salesman.new
end
# GET /salesmans/1/edit
def edit
end
# POST /salesmans
# POST /salesmans.json
def create
#salesman = Salesman.new(salesman_params)
respond_to do |format|
if #salesman.save
format.html { redirect_to #salesman, notice: 'Salesman was successfully created.' }
format.json { render :show, status: :created, location: #salesman }
else
format.html { render :new }
format.json { render json: #salesman.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /salesmans/1
# PATCH/PUT /salesmans/1.json
def update
respond_to do |format|
if #salesman.update(salesman_params)
format.html { redirect_to #salesman, notice: 'Salesman was successfully updated.' }
format.json { render :show, status: :ok, location: #salesman }
else
format.html { render :edit }
format.json { render json: #salesman.errors, status: :unprocessable_entity }
end
end
end
# DELETE /salesmans/1
# DELETE /salesmans/1.json
def destroy
#salesman.destroy
respond_to do |format|
format.html { redirect_to salesmans_url, notice: 'Salesman was successfully destroyed.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_salesman
#salesman = Salesman.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def salesman_params
params.require(:salesman).permit(:name, :address)
end
**invoice**
class InvoicesController < ApplicationController
before_action :set_invoice, only: [:show, :edit, :update, :destroy]
# GET /invoices
# GET /invoices.json
def index
#invoices = Invoice.all
end
# GET /invoices/1
# GET /invoices/1.json
def show
#invoice = Invoice.find(params[:id])
#ordenes = #invoice.ordenes
end
# GET /invoices/new
def new
#invoice = Invoice.new
end
# GET /invoices/1/edit
def edit
end
# POST /invoices
# POST /invoices.json
def create
#invoice = Invoice.new(invoice_params)
respond_to do |format|
if #invoice.save
format.html { redirect_to #invoice, notice: 'Invoice was successfully created.' }
format.json { render :show, status: :created, location: #invoice }
else
format.html { render :new }
format.json { render json: #invoice.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /invoices/1
# PATCH/PUT /invoices/1.json
def update
respond_to do |format|
if #invoice.update(invoice_params)
format.html { redirect_to #invoice, notice: 'Invoice was successfully updated.' }
format.json { render :show, status: :ok, location: #invoice }
else
format.html { render :edit }
format.json { render json: #invoice.errors, status: :unprocessable_entity }
end
end
end
# DELETE /invoices/1
# DELETE /invoices/1.json
def destroy
#invoice.destroy
respond_to do |format|
format.html { redirect_to invoices_url, notice: 'Invoice was successfully destroyed.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_invoice
#invoice = Invoice.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def invoice_params
params.require(:invoice).permit(:date, :fid, :name, :address, :salesman_id)
end
end
-davefogo
Add the following to your views instead of what you currently have<%= customer.salesman.name if customer.salesman %>
This will ensure that you're not calling name when customer doesn't have a salesman.
Try this:
<% #customers.each do |customer| %>
<%= customer.name %>
<%= customer.address %>
<%= customer.salesman.try(:name) %>
<% end %>
Do this:
<% #customers.each do |customer| %>
<% Rails.logger.debug "\n\n#{#customers} has a nil customer in it\n\n" if customer.nil? %>
<% Rails.logger.debug "\n\nCustomer #{customer.id} has no salesman for [#{customer.salesman_id}]\n\n" if customer.salesman.nil? %>
<%= customer.name %>
<%= customer.address %>
<%= customer.salesman.name %>
<% end %>
...and then check your logs after hitting the index.