Rails Custom Validation error message

Without getting into all the javascript for a textfield, I'd like the following validation:

validates_length_of :brief_description,
  :maximum=>250, 
  :message => "Brief is #{self.brief_description.length} long (max is 250)"

But the self.brief_description reference in the message doesn't work. What's the best way to do this?

I tried #{params[:brief_description].length} as well, but the m开发者_JAVA技巧odel doesn't know anything about params...

I could be wrong but I think you can try enclosing the string in single-quotes, and it might defer evaluating the string until runtime.

Short of that, you could write a custom validation (that doesn't use the validates_length_of macro) and do something like:

def validate_brief_description
  errors.add :brief_description, "Brief is #{brief_description.length} long (max is 250)" if brief_description.length > 250
end