Having trouble with create method in CommentsController - ruby-on-rails

Question

This is my current Create method in CommentsController
def create
#place = Place.find(params[:place_id])
#comment = #place.comments.create(comment_params)
#comment.user = current_user
if #comment.save
redirect_to place_path(#place)
else
render "comments/_form"
end
end
I was told by someone that this hits the database twice. Upon checking the logs, this is the result:
Started GET "/places/9" for 127.0.0.1 at 2015-01-22 15:01:47 -0800
Processing by PlacesController#show as HTML
Parameters: {"id"=>"9"}
Place Load (0.3ms) SELECT "places".* FROM "places" WHERE "places"."id" = ? LIMIT 1 [["id", 9]]
Comment Load (0.2ms) SELECT "comments".* FROM "comments" WHERE "comments"."place_id" = ? [["place_id", 9]]
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1 [["id", 2]]
CACHE (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1 [["id", 2]]
CACHE (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1 [["id", 2]]
CACHE (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1 [["id", 2]]
Rendered comments/_comment.html.erb (8.0ms)
Rendered comments/_form.html.erb (2.7ms)
Rendered places/show.html.erb within layouts/application (73.3ms)
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1 [["id", 2]]
Completed 200 OK in 532ms (Views: 529.4ms | ActiveRecord: 1.0ms)
So obviously, I don't want to be inefficient in my code.
This is what the person suggested instead:
comment_params[:user_id] = current_user.id
if #places.comments.create(comment_params)
.....
else
....
end
So ... I rewrote the Create method to this:
def create
#place = Place.find(params[:place_id])
#comment = #place.comments.create(comment_params)
comment_params[:user_id] = current_user.id
if #places.comments.create(comment_params)
redirect_to place_path(#place)
else
render "comments/_form"
end
end
Upon the rewritten Create method, I keep getting this error when I try to leave a comment: undefined method comments for nil:NilClass
Help me to understand how to rewrite this Create method correctly, please?
SideNote - Not sure if it's relevant if yes, please address it, if no, please ignore
Upon checking the last comment in the rails console, I was startled to see that the user_id is nil, whereas for place, it's not.
Place belongs to User
Comment belongs to User
User has many of both Place and Comment

Answer 1

You're calling create twice, which would result in the comment being posted twice, which is probably not what you have intended.
The first time you call create, it has no user_id assigned, that's the reason the user_id is set to null in the database (hint: use a presence validation on the user_id in your comment model).
The second time you call create you call it on #places instead of #place (typo). This causes your nil error.
Here is another way to solve your problem:
def create
#place = Place.find(params[:place_id])
#comment = #place.comments.build(comment_params)
#comment.user_id = current_user.id
if #comment.save(comment_params)
redirect_to place_path(#place)
else
render "comments/_form"
end
end
The difference is, that we first "build" a comment without creating it, but it will be filled with the ID of the place etc.
In a next step we add the current user's id and then we call save on the object, which hits the database.