Array of Hashes into dropdown in Rails

Question

In Rails, I have an array of hashes (@things) that looks something like this:

[
{"id"=>1, "name"=>"firstThing"}, 
{"id"=>2, "name"=>"secondThing"}, 
{"id"=>3, "name"=>"thirdThing"}
]

I also have an object with a thingId with a value of 2 (@otherThing.thingId = 2). I would like to turn the array into a dropdown with an empty option and with the secondThing option selected (because it has id = 2).

I successfully built this with some if, else and using that to output some <option value... code, then realized that's probably not the Railsy way to do it. Not sure exactly how to railsify this the best way. I have reviewed the documentation at http://api.rubyonrails.org/classes/ActionView/Helpers/FormOptionsHelper.html, but I'm not sure how my array of hashes fits in with all of that.

Meier · Accepted Answer · 2015-09-21 22:03:26Z

2

The options_for_select helper can take an array like this:

[
  ["firstThing", "1"],
  ["secondThing", "2"],
  ["thirdThing", "3"]
]

(The select helper uses options_for_select internally, so, depending on your use case, it makes this even simplier) So all you need is to convert your array of hashes into the above form. For example like this:

arrayForOptions = arrayOfHashes.collect { |item|
  [item['name'], item['id']]
}

edited Sep 21, 2015 at 22:03

answered Sep 21, 2015 at 21:57

Meier

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4 Comments

Ben Walker Over a year ago

OK, now I have it converted the way you're describing, but the documentation for options_for_select doesn't show how to have the correct id selected based on another variable's value. Do you know how to do that?

Meier Over a year ago

the second parameter of the options_for_select call is the id of the element that should be selected.

Ben Walker Over a year ago

Got it. In order to get a blank option, I also added .insert(0, "") on my collect.

Jeff Spicoli Over a year ago

A blank dropdown option can also be added by using this flag within the input element include_blank: true

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