reloadData in NSTableView but keep current selection

Well, you can save selection before calling reloadData and restore it after that.

NSInteger row = [self.tableView selectedRow];
[self.tableView reloadData];
[self.tableView selectRowIndexes:[NSIndexSet indexSetWithIndex:row] byExtendingSelection:NO];

This worked for me in some cases. But if you insert some items BEFORE the selected row, you should andjust your row variable by adding count of added items to it.

Swift 4.2

Create an extension and add a method which preserves selection.

extension NSTableView {

    func reloadDataKeepingSelection() {
        let selectedRowIndexes = self.selectedRowIndexes
        self.reloadData()
        self.selectRowIndexes(selectedRowIndexes, byExtendingSelection: false)
    }
}

Do this in case you use the traditional way of populating table views (not NSArrayController).