undefined method for #<Array

Question

I have this inside User model

def self.home_opinions (user) 
        home_opinions = user.opinions
        user.follows.find_each do |follow|
          home_opinions+=(follow.opinions)
        end
        home_opinions.order_by_most_recent
    end

I have this scope inside Opinion model

scope :order_by_most_recent, -> { includes(:author).order(created_at: :desc) }

It shows this error

undefined method `order_by_most_recent' for #<Array:0x00007eff64d076f8>

But when I try User.home_opinions(User.find(9)) inside rails console It works

I have two questions

why It shows the error
What are the best practices for this code maybe using includes?

ScottM · Accepted Answer · 2021-06-23 22:26:39Z

1

.order_by_most_recent will only work on an ActiveRecord::Relation.

When you call home_opinions = user.opinions you get a relation object back.

The problem comes when you call

home_opinions += follow.opinions

That action converts the relation into an array, and then .order_by_most_recent is no longer available.

If you can, you should try and get all relevant opinions in a single ActiveRecord call. That way, you'll have an ActiveRecord::Relation object which you can chain with other scopes – plus, you can do everything in a fixed number of database calls, rather than an extra call for every member of the follows association.

Try something like:

opinion_owner_ids = [user.id] + user.follow_ids
home_opinions = Opinion.where(user_id: opinion_owner_ids)
home_opinions.order_by_most_recent

edited Jun 23, 2021 at 22:26

answered Jun 19, 2021 at 18:29

ScottM

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4 Comments

Bishoy Faheem Over a year ago

def self.home_opinions (user) follows_ids = [] user.follows.find_each do |follow| follows_ids.push(follow.id) end ` ids = [user.id] + [follows_ids]` ` home_opinions = Opinion.where(author_id: ids)` home_opinions.order_by_most_recent ` end` I did that and works thank you!

Bishoy Faheem Over a year ago

Btw how to add multiple line code in a comment in stack overflow :D?

ScottM Over a year ago

You shouldn't need to construct your own array of IDs by looping through user.follows. If you've declared has_many :follows in your User model, you will automatically get a method called follow_ids that includes all the ID records. Have a look at the Example section in the Rails docs.

Bishoy Faheem Over a year ago

Yes I did that and its working thanks again ids = [user.id] + user.follow_ids home_opinions = Opinion.where(author_id: ids) home_opinions.order_by_most_recent

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