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Ruby

RoR (Intermediate) Creating the friendship form. Why not use find! instead of where?

In the video the use the following to find a user by their profile name:

@friend = User.where(profile_name: params[:friend_id]).first

Thats all fine and dandy, the problem arises that you can pass invalid friend id's because where wont raise an ActiveRecord::RecordNotFound exception if the rows are empty. So they then suggest the following:

@friend = User.where(profile_name: params[:friend_id]).first
raise ActiveRecord::RecordNotFound if @friend.nil?

Why not use the find_by_x_and_x idiom? (I know its being taken out in Rails 4).

If you do:

@friend = User.find_by_profile_name(params[:friend_id])

The same issue happens, but find has a bang format that will raise an exception if nothing is returned. You could simply do:

@friend = User.find_by_profile_name!(params[:friend_id])

to get the same behaviour? Is there a reason why this isn't idiomatic, or why they didn't want to do it this way?

2 Answers

I also wondered this, I did use find methods in the end. Seemed much cleaner to me. I also wondered why they did the hover to display delete and edit bit with CoffeeScript instead of using a much simpler, modern, CSS3 :hover subclass.

I think this was done because the find methods are being depreciated in Rails4 http://edgeguides.rubyonrails.org/4_0_release_notes.html#active-record-deprecations (even though it seems like find_by_ survived)

where returns an ActiveRecord::Relation (not an array, even though it behaves much like one), which is a collection of model objects. If nothing matches the conditions, it simply returns an empty relation.

find (and its related dynamic find_by_columnname methods) returns a single model object, or possibly a collection of model objects in an Array (not a Relation). If nothing is found, an ActiveRecord::RecordNotFound exception is raised.

Thank you Nima, I know that ActiveRecord::Relation delegates array methods to the array class when its not defined (ActiveRecord::Relation.superclass == Array). I didn't know find didn't return an AR::Relation so it seems much more obvious to me now.

glad i could be a small help :)