Best way to find a single record using ActiveRecord 3 / Arel?

Question

Where I used to do this:

Foo.find_by_bar('a-value')

I can now do this:

Foo.where(:bar => 'a-value').limit(1).first

Is this recommended? Is this the best way? Should I continue to use the "old" way because it continues to be useful syntactic sugar, or is there an Even Better way I can do that now, which will support chaining and all the other good stuff?

I actually quite like the old find_by_*. The intent is clear, and if that's all you need, the syntax is simpler. — Matthew Rudy, Jun 13 '11 at 20:04
And its still perfectly valid in Rails 3. If using Rails 4, you can use `find_by(bar: 'a-value')`. — sevenseacat, Aug 02 '13 at 15:11
I came here looking for _just_ a single record. If anyone else is after the same, I've popped an answer to this scenario [down here](https://stackoverflow.com/questions/6326440/best-way-to-find-a-single-record-using-activerecord-3-arel/66600205#answer-66600205) :) — SRack, Mar 12 '21 at 12:47

score 50 · Accepted Answer · edited Nov 22 '22 at 18:15

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Rails 4 :

Foo.find_by( bar: 'a_value', wibble: 'a wibble value' )

edited Nov 22 '22 at 18:15

Joshua Pinter

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answered Feb 10 '14 at 05:14

SureshCS

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Can you add a source for this? – l8nite Feb 24 '14 at 07:10
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Any idea why RubyMine warns that this method should not be called from view helper? – Vlad Mar 31 '15 at 19:31
find_by is kind of a heavy operation and its advisable not to trigger while rendering view – SureshCS Jul 01 '16 at 04:24

score 26 · Answer 2 · answered Jun 13 '11 at 03:49

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I think the preferable way to return a single record would be along the lines of your second example, but you can omit the limit part:

Foo.where(:bar => 'a-value').first

This follows the new syntax and supports chaining if you want to add more conditions to the lookup.

answered Jun 13 '11 at 03:49

nmunson

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Use `Foo.where(:bar => 'a-value').first!` if you want to ensure a record is found. That way `ActiveRecord::RecordNotFound` will be raised otherwise. – iltempo Mar 23 '14 at 20:05

score 6 · Answer 3 · edited Jan 20 '22 at 09:47

If you need one and only one record (which I came here looking for), Rails 7.0 introduces find_sole_by (or where(...).sole) for this.

The behaviour is as follows:

Finds the sole matching record. Raises ActiveRecord::RecordNotFound if no record is found. Raises ActiveRecord::SoleRecordExceeded if more than one record is found.

Use case is simple:

Foo.find_sole_by(bar: 'a-value')

Handy for those occasions where a single record is mandatory.

score 5 · Answer 4 · answered Aug 02 '13 at 14:52

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Rails gives you a whole load of magic methods for this kind of thing:

Foo.find_by_bar('a-value')

You can also use multiple attributes:

Foo.find_by_bar_and_wibble('a foo value', 'a wibble value')

And appending a ! causes it to throw a RecordNotFound if nothing's found:

Foo.find_by_bar!('a-value')

answered Aug 02 '13 at 14:52

Will Tomlins

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These dynamic finders are deprecated as of rails 4.0 (http://edgeguides.rubyonrails.org/4_0_release_notes.html#active-record-deprecations) so it's probably not a good habit to learn now. – Wes Oldenbeuving Feb 07 '14 at 15:58

score 2 · Answer 5 · answered Mar 11 '14 at 17:51

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Other alternative:

Foo.find(:first, conditions: { bar: 'a-value' })

You can also use multiple attributes:

Foo.find(:first, conditions: { bar: 'a-value' , wibble: 'a wibble value' })

answered Mar 11 '14 at 17:51

Victor Lellis

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Best way to find a single record using ActiveRecord 3 / Arel?

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