How do I save the user_id by adding the mail?

How do I save the user_id by adding the mail?

For the relationship, you have to save the user_id, but to be more dynamic for the user, I want to the users search other users by the email and rails save the id as usual.

How is it done?

In the views I have:

 <div class = "field">
     <% = form.label: user_id%>
     <% = form.text_field: user_id, id%>
   </ div>

 I'm using Devise.

Thanks Jack! As you said, I solve it