for ( my $i = $#{ $self->{ trolley } }; $i >= 0; --$i ) {
        if ( ${ $self->{ trolley } }[ $i ]->{ id } eq $id ) {
            $self->{ intent } = undef;
            splice @{ $self->{ trolley } }, $i, 1;
            return scalar @{ $self->{ trolley } };
        }
    }