validation.py 文件源码

def fetch_attr(cls, model, label, field):
    try:
        return model._meta.get_field(field)
    except models.FieldDoesNotExist:
        pass
    try:
        return getattr(model, field)
    except AttributeError:
        raise ImproperlyConfigured("'%s.%s' refers to '%s' that is neither a field, method or property of model '%s.%s'."
            % (cls.__name__, label, field, model._meta.app_label, model.__name__))