How to loop through model scopes to generate a listing?

Rails
1

Hello all,

I am wondering how I can loop through the scopes defined in a model. As
an
example, if I want to create an erb template that lists the content of
of a
model separated by scope with the header of that content being the scope
name, I would like to be able to do this without having to create a
specific loop for each scope.

Instead of something like

Scope1

<% Model.scope1.each do |record| %> <%= record.attribute%> <% end %>

Scope2

<% Model.scope2.each do |record| %> <%= record.attribute%> <% end %>

I would like to do something like

%w(scope1 scope2).each do |scope|

<%= scope %>

<% Model.scope.each do |record| %> <%= record.attribute%> <% end%> <% end %>

Which hopefully would give me the same output with less code. Does
anyone
have any ideas on how I might be able to accomplish this?

Thanks

2

You can use send method for calling scopes as followed:

<%- %w(scope1 scope2).each do |scope|

<%= scope %>

<%- Model.send(scope.to_sym).each do |record| %> <%= record.attribute%> <%- end%><%- end %>

Thanks,
Lauree
Ruby on Rails Developer http://www.allerin.com
Allerin Technologies

3

You can use send method for calling scopes as followed:

<%- %w(scope1 scope2).each do |scope|

<%= scope %>

<%- Model.send(scope.to_sym).each do |record| %> <%= record.attribute%> <%- end%> <%- end %>

However looping more than a scope may cause huge data to be rendered on
a
single page. I would suggest avoiding this.

Following is an way to you can avoid looping multiple scopes on a single
page:

  1. Keeping a select list on the page may help you to display only
    selective
    data. For example say you are having model User as :

class User < ActiveRecord::Base

scope :active, → { where active: true }
scope :inactive, → { where active: false }
end

Then your select list will be :

<%= select_tag(:scope_name, options_for_select([[‘All’, ‘all’],
[‘Active Users’, ‘active’], [‘InActive Users’, ‘inactive’],…])) %>

Above select list will have options of All, Active Users, InActive Users
with values as actual scope names that you are having in your model.

With JS/JQuery you can write coding to send a get request to the
controller
which you were using for displaying data. So when user will be selecting
any option the page will get reloaded. It can be done using following
code:

$(function(){
$(‘#scope_name’).change(function(){
window.location.replace(‘/users?scope_name=’+ $(this).val());
})
}

With above coding you will be getting scope_name parameter in params
in
your controller.

Use this params to retrieve records in controller only as follows:
In my controller action:

def index
@scope_name = if %w(all, active,
inactive).includes?(params[:scope_name]) # taking care that proper
scope name is passed here
params[:scope_name]
else
‘all’
end
@records = User.send(@scope_name.to_sym)
endend

Now this @records can be used on the
template(views/users/index.html.erb)
for displaying the record attributes:

<%= @scope_name.titleize %>

<%- @records.each do |record| %> <%= record.first_name%> <%- end%>

This way you will be having selective data on a page and you will not
have
to fire any query from view.

Thanks & Regards,
Lauree
Ruby on Rails Developer http://www.allerin.com
Allerin Technologies

On Wed, May 7, 2014 at 10:16 AM, Lauree Roberts