Rails: How to check if user has previously bookmarked pin? - ruby-on-rails

Question

In my app, I have pins (posts), users and bookmarks. Each user can bookmark a post for later reading. This all works great.
However, I am stuck on how to show if the user has previously bookmarked the pin, on a list of all pins? For each pin in the list, I want to do a check in my view to see if they have bookmarked it.
pin.rb (model)
class Pin < ActiveRecord::Base
belongs_to :user
has_many :bookmarks, dependent: :destroy
end
user.rb (model)
class User < ActiveRecord::Base
has_many :pins, dependent: :destroy
has_many :bookmarks, through: :pins, dependent: :destroy
end
bookmark.rb (model)
class Bookmark < ActiveRecord::Base
belongs_to :user
belongs_to :pin
validates :pin_id, uniqueness: { scope: :user_id, :message => "has already been bookmarked" }
end
A user can bookmark a pin, which creates a single record in the bookmarks table. The bookmarks table stores the user_id and the pin_id.
I'm having a bit of a brain melt-down on how I would go about checking in the view, if a user has bookmarked a pin or not. I'd basically just like to show a yes or no flag to the user.
Any guidance or advise would be greatly appreciated.
Thanks,
Michael.
UPDATE:
I ended up modifying the anser by Lucas. In my Pin model I defined a boolean method:
def bookmarked_by?(user)
return true if bookmarks.any? {|b| b.user == user }
end
...that will return true if any bookmarks belong to the given user on this pin. Seems to work okay, but welcome any additional improvements.

Answer 1

Well I'd suggest that when you query Pins, include their Bookmarks that are associated with the current user. And then check if the Pin has any bookmarks.
pins = Pin.includes(:bookmarks).where("bookmarks.user_id" => current_user.id)
Now when looping these pins to view them, check whether the pin.bookmarks.length is 0 or more. And on that basis you can view yes or no.
<% pins.each do |p| %>
<%= "yes" if p.bookmarks.length > 0 %>
<% end %>

Answer 2

What I would do, to build slightly on #Tamer's answer is to create a method on the Pin model:
class Pin < ActiveRecord::Base
# ...
def bookmarked?
!bookmarks.empty?
end
end
Then you can simply do this in the view:
<% pins.each do |p| %>
<%= "yes" if p.bookmarked? %>
<% end %>
The main reason for this is it encapsulates the logic for understanding whether or not something is bookmarked to the thing that cares about that information, which is the pin. It also keeps logic out of the view, which is super important for clean and maintainable views.
What if, for example, you wanted to check and show pins as bookmarked only if bookmarked by the current user, you could do something like the following:
class Pin < ActiveRecord::Base
# ...
def bookmarked_by?(user)
return false unless bookmarked?
bookmarks.any? {|b| b.user == user }
end
end
I don't like the bookmarks.any? call as I think it will cause another db query, and I think there's a better way to do it, offhand, I'm unsure. I'll update once I find it.
However, in the view, you can now do:
<% pins.each do |p| %>
<%= "yes" if p.bookmarked_by? current_user %>
<% end %>
Update:
Was given an incredibly efficient way for distilling the query down into a COUNT query:
class Pin < ActiveRecord::Base
def bookmarked_by?(user)
bookmarks.for_user(user).any?
end
end
class Bookmark < ActiveRecord::Base
scope :for_user, ->(user) { where(user: user) }
end
pins = Pin.includes(:bookmarks) # ... any additional conditions
<% pins.each do |pin| %>
<%= 'yes' if pin.bookmarked_by? current_user %>
<% end %>
See the question I posted here with the brilliant answer from #pdobb: How does Rails handle a has_many when query uses includes?

Answer 3

Maybe this?
<%= "yes" if Bookmark.where(pin_id: pin.id, user_id: current_user.id).first %>
Probably cleaner to make a helper method, or maybe a Pin class method
class Pin
def bookmarked?(user)
!!Bookmark.where(pin_id: id, user_id: user.id).first
end
...
in the view...
<%= "yes" if pin.bookmarked?(current_user) %>