Difference between .find and .find_by in Rails 4

I have received multiple identical questions from my readers, so I think it would make sense to dedicate a separate post to this issue.

What is the difference between this:

User.find(1)

vs

User.find_by_id(1)

and when to use one over the other ?

Great Question! The answer to this question lies in how they are handling exceptions.

When you use .find_by_id and object is not found, you won’t get an exception.

So code like this :

begin
  user = User.find_by_id(1)
rescue ActiveRecord::RecordNotFound => e
  error_count += 1
end
#error_count is 0

Will never reach your rescue block, because .find_by_id will just evaluate to nil.

Whereas this code:

begin
 user = User.find(1)
rescue ActiveRecord::RecordNotFound => e
 error_count += 1
end
#error_count is 1

will work out of the box because .find will raise an exception if record is not found.

Note: Workaround if you want to use find_by and raise an exception to use ‘!’:

user = User.find_by_id!(1)

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Cheers,

Anatoly

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