Dynamic bang finders in Rails 4

rubyonrails-core
1

Hi,

I propose to add #where! finder that raises an exception if the relation is empty like find_by_xxx! method in Rails3.

Rails 4 is getting rid of dynamic finders, so

User.find_by_hash(hash)

becomes

User.where(hash: hash) # .first

Okay, not a big deal. But what is the best way to deal do with dynamic bang finders like User.find_by_hash!(hash) since there is no where!() method?

A suggestion I got on Stackoverflow (Dynamic bang finders in Rails 4 - Stack Overflow) is to add a #where! method.

If you need a method that finds all but raises exception if the relation is empty, you can create such new method for your models yourself (or mixin to ActiveRecord::QueryMethods). Something like:

def where!(*args)

	  rel = where(*args) 

	  raise RecordNotFound if rel.empty?

	  rel

end
2

No, those ‘dynamic finders’ based on your attribute names aren’t get removed. If you have an attribute name hash, you should be able to still do User.find_by_hash!

See the list of deprecated methods here: http://edgeguides.rubyonrails.org/4_0_release_notes.html#active-record-deprecations

-Prem

3

Wouldn’t it be more intuitive to use the #first! method for this purpose?

i.e., User.find_by_hash!(hash) is the same as User.where(hash: hash).first!

I know that I often chain where conditions together (especially when using scopes), so it makes sense to raise the exception only when I actually try to fetch the record from the database.

4

or User.find_by! hash: hash

http://edgeapi.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find_by-21

Francesco Rodríguez "The Most Powerfull Rookie"

@frodsan (http://twitter.com/#!/frodsan) frodsan (Francesco) · GitHub http://www.frodsan.com/

5

Oh, right “All dynamic methods EXCEPT for find_by_... and find_by_...! are deprecated.”

Either the pages has changed since or I was blind when reading it.