This article was originally posted on my blog.
Sometimes an array of data needs to be submitted in an HTML form. A form to send invites to a bunch of users for example. That'd just be a series of email fields; and in the controller; we'd want an array of the emails to iterate over and send invites.
Rails form helpers are set up to have a key and value for each field, so it's not immediately obvious how to send an array of data. But in Rails, there's always a way!
If we append []
to the name
of a field, it'll be parsed as an array! So for an array of emails to send invites; setting name
as invites[]
on all the email fields and gives us an array in the controller.
To generate the form, we can use the following code:
<%= form_with(scope: :invites, url: invite_path) do |form| %>
<% 3.times do %>
<!-- id has to be nil to prevent clashes as all fields would have the same id -->
<%= form.email_field nil, id: nil, placeholder: "Email Address" %>
<% end %>
<%= form.submit %>
<% end %>
Passing nil
as the first argument to email_field
instead of a name gives us the []
we need for an array. The generated markup looks like:
<form action="/invite" accept-charset="UTF-8" data-remote="true" method="post">
<input type="hidden" name="authenticity_token" value="....">
<input placeholder="Email Address" type="email" name="invites[]">
<input placeholder="Email Address" type="email" name="invites[]">
<input placeholder="Email Address" type="email" name="invites[]">
<input type="submit" name="commit" value="Save Invites" data-disable-with="Save Invites">
</form>
On the controller, we can use the submitted data as:
def create
invited_users = params.require(:invites)
p invited_users
# => ["a@example.com", "b@example.com", "c@example.com"]
end
To permit an array parameter in a nested form field, we can use the following pattern:
params.require(:product).permit(tags: [])
It's a little unintuitive but submitting arrays from a form can be a useful tool in your toolbox!
Top comments (2)
what is the difference of your approach and using "multiple: true" ?
<%= form.email_field :email, multiple:true, placeholder: "Email Address" %>
The
multiple
option relies on the user knowing that they have to provide a comma separated list of email addresses. That's not user friendly in my book. Also, if you do that, Rails parses it into an Array with a single string of the comma separated emails:"email"=>["a@example.com, b@example.com"]
This means you'd need to do some processing on the server before updating the record. You couldn't just pass the parameters through to Active Record.
Do that make sense?