class TrustyCms::Config::Definition

* if :allow_blank has been set to false, we test that the value is not blank
* if the config item is a selector we test that its value is one of the permitted options
* if :type is :integer, we test that the supplied string resolves to a valid integer
* if :validate_with specifies a block, the setting object is passed to the block
There are several ways in which validations might be defined or implied:
Checks the supplied value against the validation rules for this definition.

def validate(setting)
  if allow_blank?
    return if setting.value.blank?
  else
    setting.errors.add :value, :blank if setting.value.blank?
  end
  if validate_with.is_a? Proc
    validate_with.call(setting)
  end
  if selector?
    setting.errors.add :value, :not_permitted unless selectable?(setting.value)
  end
  if integer?
    Integer(setting.value) rescue setting.errors.add :value, :not_a_number
  end
end