Whats a good way to avoid nil lookup errors

rubyonrails-talk
1

When navigating to: http://localhost:3000/users/12

Whats a good way of avoiding the error: "Couldn't find User with ID=12", which happens when i try to display a page of user_id 12 that doesnt exist in the database.

Instead of showing the error. id like to show a page that says: "This user does not exist"

Someone suggested using rescue_from. Is this the best solution for this? Or are there better alternative approaches?

2

def show   @user = User.find(params[:id]) rescue ActiveRecord::RecordNotFound   redirect_to users_path, :alert => "This user does not exists" end

3

One of the solutions would be to use redirect_to and flash[:notice] like:

@user = User.find(1) unless @user   flash[:notice] = "can't find user with given id"   redirect_to users_path end

I won't say it's the best but it's still a solution :slight_smile:

4

Yes but, it will never reach "unless." The system fails after @user = User.find(1) since Active Record is trying to find a record that does not exists

5

@user = User.find(1) if User.exists?(1)

I don't like doing two lookups for one record, but it works

6

What about @user = User.find(:first, :conditions => {:id => 1}) if (@user)    blah, blah, blah end

It's longer to type, but returns nil if the user doesn't exist.

7

Ugis almost has it. Try this

@user = User.find_by_id(1) unless @user   flash[:notice] = "can't find user with given id"   redirect_to users_path end

ActiveRecord::Base#find_by_id is a dynamic finder that will work just like the line Simon has above--nil if there is no record found.

-Rob

Rob Biedenharn Rob@AgileConsultingLLC.com http://AgileConsultingLLC.com/ rab@GaslightSoftware.com http://GaslightSoftware.com/

8

So this would be the convention right? not by using rescue_from. Is this right?

9

Hi Christian

10

Hi Paul. but wouldnt that redirect to users_path on any activerecord not found event?

11

Good call on that find_by_id. Noted to myself :slight_smile:

12

nope, only within the action.