Using if statements on multiple instance variables in one view - Rails

Question

I'm building a rails app where a user model has several has_many relationships with other models.

class User < ActiveRecord::Base

    has_many :model_2s
    has_many :model_3s
    has_many :model_4s

end

I am then creating a profile page where I display data from each of these models for the current user. I am doing this using a separate controller - profiles_controller.rb

In the profiles controller I am creating instance variables for each of these models based on the current user:

class ProfilesController < ApplicationController

    @user = User.find(params[:id])
    @model_2s = @user.model_2s.all
    @model_3s = @user.model_3s.all
    @model_4s = @user.model_4s.all
end

I am then able to display data from these instance variables in the show view for profiles. I do this by calling an each method.

The functionality I am now trying to add is to show some default data (like Lorem Ipsum placeholder text) for fields that the user has not filled in.

My issue is that I cannot figure out how to check if a particular field in these instance variables is empty.

For example, I would like something along the lines of:

<% if @model_2s.field_1.empty? %>
    <p>Lorem Ipsum</p>
<% else %>
    <%= @model_2s.field_1 %>
<% end %>

However this gives an "undefined method 'field_1'... " error.

I know how to check for @model_2s.any? to confirm the instance variable itself is present, but I want to be able to do a conditional check at the next level down - the fields within the instance variable.

@model_2s is an enumerable (array). You can test it's empty with @model_2s.empty? or you can test a particular element with @model_2s.first.field_1.blank? (here the first element is checked) — Baldrick
– Baldrick, Commented May 27, 2013 at 8:09
thanks... unfortunately after adding '.first' I still get the same error... "undefined method 'field_1'... " — mgtcampbell
– mgtcampbell, Commented May 27, 2013 at 8:15
Then your @model_2s array is empty. You will first have to check whether anything is found at all, probably by doing something like if @model_2s.empty? || @model_2s.first.field_1.blank?. — Jaap Haagmans
– Jaap Haagmans, Commented May 27, 2013 at 8:39
@JaapHaagmans - model_2s is not empty, I am able to loop over it and pull out other fields. I think the issue as per the answers below is that I was trying to do the if outside of an each loop. — mgtcampbell
– mgtcampbell, Commented May 27, 2013 at 10:30

mihai · Accepted Answer · 2013-05-27 09:17:17Z

1

Not sure what you're doing in your view, but definitely you need to loop each of those result sets if you want to access something like field_1

<% @model_2s.each do |m| %>

    <% if m.field_1.empty? %>
        <p>Lorem Ipsum</p>
    <% else %>
        <%= m.field_1 %>
    <% end %>

<% end %>

This also handles the case when @model_2s is empty.

answered May 27, 2013 at 9:17

mihai

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2 Comments

mgtcampbell Over a year ago

Great, thanks. Couple of questions - 1. Is there an easy explanation as to why you can only access the fields of an instance variable by using an each loop? and 2. If I need to do this over a number of models in my view, should I be setting them up as helper methods?

mihai Over a year ago

1) because you're working with an array (actually an ActiveRecord::Relation which behaves as an Array), and the way you deal with arrays is usually by looping :). 2) yes, of course, you can use helper methods to clean up the view code

Thaha kp · Accepted Answer · 2013-05-27 09:28:19Z

0

Try this way

<% if @model_2s %>
 <% @model_2s.each do |model_2| %>
  <% if model_2.field_1.empty? %>
      <p>Lorem Ipsum</p>
  <% else %>
      <%= model_2.field_1 %>
  <% end %>
 <% end %>
<% end %>

It will be inside the loop..

edited May 27, 2013 at 9:28

answered May 27, 2013 at 9:05

Thaha kp

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2 Comments

Manoj Monga Over a year ago

you can not call field_1 on an enumerable. may be you can loop through @model_2s to get the object, the method/attribute (field_1) is defined for.

mgtcampbell Over a year ago

thanks @Thahakp - seems the same point as the other answer - I needed to be looping through the instance variable.

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