Question

I have simple select field

f.select(:name, [["- Choose Name -", 0]] + People.all.map{ |c| [c.name, c.id] }) 

How can I validate, if some name was selected?
I tried this rule:

  validates :name, :presence => {:message => 'Name cannot be blank.'}

But if I send form without choosing the name, the form is sent…

So I would like to ask you, how can I validate the select field?

Answer 1

In your example, people are selecting a name, they’re selecting the name - Choose Name - with id 0.

If you want to give an option that doesn’t correspond to a real choice then you have two options:

f.select(:name, People.all.map{ |c| [c.name, c.id] }, :include_blank => "- Choose Name -")

f.select(:name, People.all.map{ |c| [c.name, c.id] }, :prompt => "- Choose Name -")

These are basically identical. Both will display an option at the top of the select which won’t result in a value being set. However, the prompt version will only display this extra option if there isn’t a current value selected, i.e. if used on an edit form it won’t let the user clear their selection by setting it back to nil

Note that the include_blank method is very similar to the following code, except lots more readable:

f.select(:name, [["- Choose Name -", nil]] + People.all.map{ |c| [c.name, c.id] })