Custom schematics type.

custom_schematics_type.py

class EventId(types.BaseType):
    """Schema type for aggregate event id."""
    DIVIDER = ':'

    def to_primitive(self, value):
        if not isinstance(value, tuple):
            raise ValidationError('{0} is not a tuple'.format(value))
        if len(value) != 2:
            raise ValidationError('{0} does not have two items'.format(value))
        prim = EventId.DIVIDER.join(str(v) for v in value)
        return prim

    def convert(self, value):
        if not isinstance(value, basestring):
            raise ValidationError('{0} is not a string'.format(value))
        pieces = value.split(EventId.DIVIDER)
        if len(pieces) != 2:
            raise ValidationError(("{0} had more than one"
                                   " dividers.").format(value))
        datastruct = tuple(pieces)
        return datastruct