How to simplify query - ruby-on-rails

Question

I have a controller method for searching and listing invoices, sales orders and homes based on params name, how to simplify this index method`
def index
#so = QbwcSalesOrder.paginate(:page => params[:page], :per_page => 30)
if params[:qs] == "Sales Orders"
#so = #so.where("ref_number = ? ",params[:keyword]) if params[:keyword].present?
elsif params[:qs] == "Invoices"
#so = QbwcInvoice.paginate(:page => params[:page], :per_page => 30)
#so = #so.where("ref_number = ? ",params[:keyword]) if params[:keyword].present?
elsif params[:qs] == "All Homes"
#so = QbwcHome.paginate(:page => params[:page], :per_page => 30)
elsif params[:qs] == "Existing Homes"
#so = QbwcHome.where(record_type: "FromQB").paginate(:page => params[:page], :per_page => 30)
end
end

Answer 1

First of all unify hash syntax and indentation, it's hard to read.
Second paginate once at the end of the index method, looks like you paginate always the same way.
Third think about scopes or query object https://mkdev.me/en/posts/how-to-use-query-objects-to-refactor-rails-sql-queries
Here is simplified version, you can use it in index or move to the query object:
def index
#so = QbwcSalesOrder.all
#so = #so.where("ref_number = ? ", params[:keyword]) if params[:keyword] && params[:qs] == "Sales Orders"
#so = #so.where("ref_number = ? ", params[:keyword]) if params[:keyword] && params[:qs] == "Invoices"
#so = #so.where(record_type: "FromQB") if params[:qs] == "Existing Homes"
#so = #so if params[:qs] == "All Homes"
#so = #so.paginate(page: params[:page], per_page: 30)
end

Answer 2

To me this looks like the method is doing way to much and needs to be split into managable parts:
def index
#so = qs_model_scope(params[:qs])
.paginate(page: params[:page], per_page: 30)
.then do |scope|
filter_by_keyword(scope)
end
end
# ...
private
def qs_model_scope(qs)
case qs
when "Invoices":
QbwcInvoice.all
when "All Homes":
# Smelly - should be a model scope
QbwcHome.where(record_type: "FromQB")
else
QbwcSalesOrder.all
end
end
def filter_by_keyword(scope)
if params[:keyword].present? && ["QbwcSalesOrder","QbwcInvoice"].include?(scope.model.name)
# no need to use a SQL string
scope.where(ref_number: params[:keyword])
else
scope
end
end
If the complexity of this continues to grow you should consider moving this filtering process out of the controller and into a separate object (such as a form object or service object or just a PORO) so that it can be tested in isolation.

Answer 3

I'd split the logic into separate methods. As already mentioned in another answer it makes sense to move it to a query object or something.
def index
scope = invoices || all_homes || existing_homes || sales_orders
#so = scope.paginate(:page => params[:page], :per_page => 30)
end
private
def invoices
return if params[:qs] != 'Invoices'
return QbwcInvoice if params[:keyword].blank?
QbwcInvoice.where(ref_number: params[:keyword])
end
def all_homes
QbwcHome if params[:qs] == 'All Homes'
end
def existing_homes
QbwcHome.where(record_type: 'FromQB') if params[:qs] == 'Existing Homes'
end
def sales_orders
if params[:qs] == 'Sales Orders' && params[:keyword].present?
QbwcSalesOrder.where(ref_number: params[:keyword])
else
QbwcSalesOrder
end
end