Question

In my controller i am merging the results of two different instance variables into one instance variable and i got an following error:

undefined method `<<' for nil:NilClass

Here is my controller code

  @conversational = InterestType.where("institution_id = ? or global = ? and category_id = ?", current_user.profile.institution_id, true, 1).first

    @commercial = InterestType.where("institution_id = ? or global = ? and category_id = ?", current_user.profile.institution_id, true, 2).limit(17)

    @user_interest_types << @conversational

    @user_interest_types << @commercial

How can i get over of this error or what is the good way to get following result.

1. I want to display first conversational interest type then other 17 commercial interest types.

Answer 1

If you want to append to an array you have two options and here you must pay attention to what you’re adding:

# Define an empty array
@user_interest_types = [ ]

# Add a single element to an array
@user_interest_types << @conversational

# Append an array to an array
@user_interest_types += @commercial

If you use << for both operations you end up pushing an array into an array and the resulting structure has multiple layers. You can see this if you call inspect on the result.