Custom validation functions for mapper field

MappedFieldValidations.scala

class Test extends LongKeyedMapper[Test] ...
{
  ...
  
  object data MappedString(this, 32)  { 
    
    def validateFormat(s: String) = 
      if (s.matches("[a-z0-9_]+")) Nil
      else List(FieldError(this, "Format is not valid!"))
      
    override def validations = validateFormat _ :: Nil
    
  }
  
  ...
  
}