I have a simple validation class:

```
class MappingValidator

    def validate(mapping)

    end

    protected

    def validate_presence_of_title(mapping)
      ...
    end

    def validate_presence_of_key(mapping)
      ...
    end

    def validates_class_exists(mapping)
      ...
    end

  end

```

In the `validate` method I would like to call any method starting with `validate_` and pass `mapping` as the parameter. This needs to work for subclasses of `MappingValidator` too, so that if a subclass declares a method starting with `validate_` it will also be called when validate is called on a subclass instance. Order of calls is irrelevant.