public function build_postarr( $id = null ) {
		$postarr = array(
			'tax_input'  => array(),
			'meta_input' => array(),
		);

		/*
		 * The check is lax here by design: we leave space for the client code
		 * to use this method to build post arrays; when this is used by the
		 * repository the integrity of `$id` is granted.
		 */
		$is_update = null !== $id && is_numeric( $id );

		// But still let's provide values that make sense.
		if ( $is_update ) {
			$postarr['ID'] = (int) $id;
		}

		foreach ( $this->updates as $key => $value ) {
			if ( is_callable( $value ) ) {
				$value = $value( $id, $key, $this );
			}

			// Allow fields to be aliased
			$key = Tribe__Utils__Array::get( $this->update_fields_aliases, $key, $key );

			if ( ! $this->can_be_updated( $key ) ) {
				throw Tribe__Repository__Usage_Error::because_this_field_cannot_be_updated( $key, $this );
			}

			if ( $this->is_a_post_field( $key ) ) {
				if ( $this->requires_converted_date( $key ) ) {
					$this->update_postarr_dates( $key, $value, $postarr );
				} else {
					$postarr[ $key ] = $value;
				}
			} elseif ( $this->is_a_taxonomy( $key ) ) {
				$taxonomy = get_taxonomy( $key );
				if ( $taxonomy instanceof WP_Taxonomy ) {
					$postarr['tax_input'][ $key ] = Tribe__Utils__Array::list_to_array( $value );
				}
			} else {
				// it's a custom field
				$postarr['meta_input'][ $key ] = $value;
			}
		}

		return $postarr;
	}