Gtk.TreeSelection.prototype.get_selected

function get_selected():Boolean {
    // Gjs wrapper for gtk_tree_selection_get_selected()
}

Sets iter to the currently selected node if selection is set to #GTK_SELECTION_SINGLE or #GTK_SELECTION_BROWSE. iter may be NULL if you just want to test if selection has any selected nodes. model is filled with the current model as a convenience. This function will not work if you use selection is #GTK_SELECTION_MULTIPLE.