Ruby on Rails - Group posts and sum prices - ruby-on-rails-4

Question

In my application I have models Visits & Post &
class Visit < ActiveRecord::Base
belongs_to :post, :counter_cache => true
class Post < ActiveRecord::Base
has_many :visits
When a visitor visits a post, I am adding it to my visits table with post_id and price (price is decimal).
In my dashboard, I want to show which posts they have viewed (grouped) and how much they have earned.
For instance:
1) post 1, viewed 54 times and earned $1.6, 2) post 2, viewed 39 times and earned $1.1, etc
I have tried with:
- a = Visit.group(:post_id).where(user: current_user).sum(:price)
- a.each do |n|
%p
= n
This gives me, each post_id, but price is just * BigDecimal:7fb2625f9238,'0.15E1* & I can't find post title by doing n.post.title & n.post.title gives me error: undefined method 'post'
This is result I get:
[44, #<BigDecimal:7fb2625f9238,'0.15E1',18(36)>]
[45, #<BigDecimal:7fb2625f8dd8,'0.13E1',18(36)>]
[46, #<BigDecimal:7fb2625f8928,'0.3E-1',9(36)>]
I have also tried with:
- Visit.select([:post_id, :price]).where(user: current_user).each do |e|
%p
= e.post.title
= e.cpc_bid
This option gives me all the posts and prices individually and not combined.
Results are like:
Post title 1, 0.15
Post title 1, 0.01
Post title 2, 0.1
Post title 1, 0.15
Post title 2, 0.1
Post title 2, 0.1
Post title 2, 0.1
Post title 1, 0.15
I also tried with:
- Visit.select([:post_id, :price]).group(:post_id).where(user: current_user).each do |e|
%p
= e.post.title
= e.price
This option gives me only one of the visits on the post with its price.
Results are:
Post title 2, 0.1
Post title 1, 0.15
My last try was:
- Visit.joins(:post).group(:post_id).select('sum(price) as earnings', :post_id, :title, 'count(visits.id) as total_views').where(user: current_user).each do |e|
%p
= e.title
= e.price
This gives me this error:
PG::GroupingError: ERROR: column "posts.title" must appear in the GROUP BY clause or be used in an aggregate function
LINE 1: ...ECT sum(price) as earnings, "visits"."post_id", "title", c...
How can I combine them together with sum of price on all post, with its post title.

Answer 1

You need to join tables and group
Post.joins(:visits).group(:id)
.where(visits: { user_id: current_user.id})
.select("*, sum(price) as total_price, count(visits.id) as total_views")
It adds to post instance accessors total_price and total_views.

Answer 2

Answer from #MikDiet works perfectly, only issue I had was that I was getting error from PostgreSql:
PG::GroupingError: ERROR: column "posts.title" must appear in the GROUP BY clause or be used in an aggregate function
LINE 1: ...ECT sum(price) as earnings, "visits"."post_id", "title", c...
and I changed it to:
Visit.joins(:post).group([:post_id, :title]).select('sum(cpc_bid) as earnings', :post_id, :title, 'count(visits.id) as total_views').where(influencer: current_user)
And it worked.
NB: I couldn't find the answer without #MikDiet's help and all credits goes to him