Ruby on Rails

I came across some posts which postulate that it's undesirable to
share helper methods across controller and views because UI code
(designed to render HTML) should be separate from controller code
(designed for handling requests). That makes sense but there are
times, a good example is filtering, when it only makes sense to create
a reusable method to query against the params hash from both
controller and view. For example, I created some custom filtering and
sorting. When a http request is initially made, my controller must be
able to query the database for results without user input.


# controller layer (query a default without user input)
helper_method :sort_column, :sort_direction, :for_selected_month, :for_selected_year
def driver_reports_table
@drivers = Driver.select("drivers.*,
#{sort_column}").joins([:reports, :driving_habits]).by_month(for_selected_month.to_i,
for_selected_year.to_i).order(sort_column + " " +
sort_direction).page(params[:page]).per(10)
@unit = current_unit
respond_to do |format|
format.html { render :partial => '/home/reports/
driver_reports_table', :layout => false, :locals => { :drivers =>
@drivers, :unit => @unit } }
format.json { render :json => @drivers}
end
end


private

def sort_column
if legal_attributes.include? params[:order]
params[:order]
else
"drivers.id"
end
end

def sort_direction
%w[asc desc].include?(params[:direction]) ? params[:direction] :
"asc"
end

def for_selected_month
(params[:date] && params[:date][:month]) || Time.now.month
end

def for_selected_year
(params[:date] && params[:date][:year]) || Time.now.year
end

def legal_attributes
@columns ||= Driver.column_names + DrivingHabit.column_names
end

In my view layer, the user will interact with form elements and links
to modify the values of the params hash
In one situation, I have a form tag where the user will set the date
and date and month/year attributes of the params hash:
#view
= form_tag driver_reports_path, :method => 'get', :id =>
'drivers_filter' do
%fieldset.filter_tab
= select_month(Date.today)
= select_year(Date.today, :start_year => 2012, :end_year =>
Time.now.year)
= submit_tag "Filter Date"
= render '/home/reports/driver_reports_table'

In another situation, I have links where the user will set the sort
and direction attributes of the params hash, depending on which link
they click:
#partial
= hidden_field_tag :sort, params[:sort]
= hidden_field_tag :direction, params[:direction]
...
%table.sortable
%tr
= sortable "id", :order => "drivers.id"

#helper
def sortable(column, query_string={})
title ||= column.titleize
query_string[:order] = query_string[:order] || column
css_class = 'driver_refresh'
css_class << (column ==
sort_column.gsub("driving_habits.","").gsub("drivers.","") ? " current
#{sort_direction}" : "")
query_string[:direction] = column ==
sort_column.gsub("driving_habits.","").gsub("drivers.","") &&
sort_direction == "asc" ? "desc" : "asc"
query_string[:page] = nil

content_tag :th, link_to(title,
driver_reports_path(params.merge(query_string)), {:class =>
css_class })
end

Each of the situations compensate for the other. If the user selects
an option from the select tag and thus populates the date attributes,
when they click a link, it will merge the date attributes from the
form with the link attributes that were selected and thus send them
together to the server. Conversely, when the form is submitted,
because of the hidden field tags with the current value of the sort
and direction attributes stored in them, those attributes will be send
with the form attributes.

As you can see, my view helper makes use of the sort_column and
sort_direction methods to check the current values in the params hash
to determine how to render the links. So those methods have importance
both in the controller and view layer. So it would make sense to
define the methods once and reuse them in both layers. So what is
wrong with this technique and how else could it be done so as not to
violate the MVC structure and separation of concerns?

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