undefined method `each' for nil:NilClass on an erb array iteration - ruby-on-rails

Question

Im currently working in an Rails 5 application where you can search for a first name or last name and records of the customers of that account would be displayed. However I am getting a Nil object return from search algorithm.
customers_controller:
class CustomersController < ApplicationController
def index
if params[:keywords].present?
#keywords = params[:keywords]
customer_search_term = CustomerSearchTerm.new(#keywords)
#customer = Customer.where(
customer_search_term.where_clause,
customer_search_term.where_args).
order(customer_search_term.order)
else
#customers = []
end
end
end
As you can see if there is no records found is suppose to return an empty array but is returning a Nil object.
customers/index.html.erb
[![<header>
<h1 class="h2">Customer Search</h1>
</header>
<section class="search-form">
<%= form_for :customers, method: :get do |f| %>
<div class="input-group input-group-lg">
<%= label_tag :keywords, nil, class: "sr-only" %>
<%= text_field_tag :keywords, nil,
placeholder: "First Name, Last Name or Email Address",
class: "form-control input-lg" %>
<span class="input-group-btn">
<%= submit_tag "Find Customers", class: "btn btn-primary btn-lg" %>
</span>
</div>
<% end %>
</section>
<section class="search-results">
<header>
<h1 class="h3">Results</h1>
</header>
<table class="table table-striped">
<thead>
<tr>
<th>First Name</th>
<th>Last Name</th>
<th>Email</th>
<th>Joined</th>
</tr>
</thead>
<tbody>
<% #customers.each do |customer| %>
<tr>
<td><%= customer.first_name %></td>
<td><%= customer.last_name %></td>
<td><%= customer.email %></td>
<td><%= l customer.created_at.to_date %></td>
</tr>
<% end %>
</tbody>
</table>
</section>][1]][1]

Answer 1

The first thing you should understand is that instance variables return nil if they haven't been set. If you say #fake_var == nil it will be true if you never defined #fake_var before this. You can contrast this with regular local variables, which will raise a NoMethodError if you try and use them before they're defined. For example, puts(fake_var) will raise a NoMethodError for fake_var.
Now look at your template. No matter what it will loop over #customers. If #customers has not been set, you'll see a NoMethodError because you can't call each on nil.
Finally, look at your controller action:
def index
if params[:keywords].present?
#keywords = params[:keywords]
customer_search_term = CustomerSearchTerm.new(#keywords)
#customer = Customer.where(
customer_search_term.where_clause,
customer_search_term.where_args).
order(customer_search_term.order)
else
#customers = []
end
end
Specifically the case when params[:keywords].present?. You never set #customers in this case so it will be nil when the template tries to access it.
I think if you simply replaced #customer = with #customers = it would solve your problem.

Answer 2

you can force it to return array using #to_a which converts nil to empty array
def index
return [] unless params[:keywords]
#keywords = params[:keywords]
customer_search_term = CustomerSearchTerm.new(#keywords)
#customer = Customer.where(
customer_search_term.where_clause,
customer_search_term.where_args).
order(customer_search_term.order
).to_a
end
https://apidock.com/ruby/Array/to_a