Validates presence of THIS or THAT

Question

I have a form where the user is prompt to enter a title and either :this or :that . A user can't enter both fields.

<% f.input :title%>
<% f.input :this %>
<% f.input :that%>

for my :title i have in my Model

validates :title, :presence => true

How can i pass a validation for either :this or :that

Answer 1

You can do this

validates :that, :presence => true, :if => Proc.new {this.blank?}
validates :this, :presence => true, :if => Proc.new {that.blank?}

Answer 2

Wouldn't just the first line be sufficient?

validates :that, :presence => true, :if => Proc.new {this.blank?}

If 'this' is blank and so is 'that', the first line would fail validation, so you wouldn't need the second line.