Question

我使用带有Realm结果的UITableView作为它的数据源。结果使用领域通知进行注册，并在发生更改时更新。但是，同一个表视图有一个搜索栏，可根据用户搜索查询过滤结果。这也可以正常工作，但如果通知侦听器识别出更新，则节和行计数不匹配。这样做的正确方法是什么？是否可以更新NotificationToken？

这是初始化通知令牌的代码：

let realm = try! Realm()

results = realm.objects(Person.self).filter("active = '1'").sorted(byProperty: "name", ascending: true)

// Observe Results Notifications
notificationToken = results?.addNotificationBlock { [weak self] (changes: RealmCollectionChange) in

    guard let tableView = self?.tableView else { return }
    switch changes {
    case .initial:
        // Results are now populated and can be accessed without blocking the UI
        tableView.reloadData()
        break
    case .update(_, let deletions, let insertions, let modifications):

        // Query results have changed, so apply them to the UITableView
        tableView.beginUpdates()

        tableView.insertRows(at: insertions.map { IndexPath(row: $0, section: 0) }, with: .automatic)

        tableView.deleteRows(at: deletions.map { IndexPath(row: $0, section: 0) }, with: .automatic)
        tableView.reloadRows(at: modifications.map { IndexPath(row: $0, section: 0) }, with: .automatic)
        tableView.endUpdates()
        break
    case .error(let error):
        // An error occurred while opening the Realm file on the background worker thread
        print("Error: \(error)")
        break
    }
}

此代码根据用户搜索输入更新结果：

func updateSearchResults(for searchController: UISearchController) {

    let searchText = searchController.searchBar.text!

    if searchText.isEmpty == false {

        results = results?.realm?.objects(Person.self).filter("active = '1'")

        results = results?.filter("name BEGINSWITH[c] %@ OR lastName CONTAINS[c] %@", searchText, searchText)

        results = results?.sorted(byProperty: "name", ascending: true)

        self.tableView.reloadData()

    }
    else {

        results = results?.realm?.objects(Person.self).filter("active = '1'").sorted(byProperty: "name", ascending: true)

        self.tableView.reloadData()
    }
}

如果搜索qwuery已经执行并且在更新领域数据库之前，则会发生NSRange异常。

Answer 1

您在results中覆盖updateSearchResults()。通知和notificationToken与特定的Results对象和查询相关联。因此，如果您通过其他查询覆盖results，则应停止先前的通知，然后向新的results对象重新添加通知。

所以updateSearchResults()方法应如下所示：

func updateSearchResults(for searchController: UISearchController) {
    let searchText = searchController.searchBar.text!
    if searchText.isEmpty == false {
        results = results?.realm?.objects(Person.self).filter("active = '1'")
        results = results?.filter("name BEGINSWITH[c] %@ OR lastName CONTAINS[c] %@", searchText, searchText)
        results = results?.sorted(byProperty: "name", ascending: true)
    }
    else {
        results = results?.realm?.objects(Person.self).filter("active = '1'").sorted(byProperty: "name", ascending: true)
    }

    notificationToken.stop()
    notificationToken = results?.addNotificationBlock { [weak self] (changes: RealmCollectionChange) in
        guard let tableView = self?.tableView else { return }
        switch changes {
        case .initial:
            tableView.reloadData()
            break
        case .update(_, let deletions, let insertions, let modifications):
            tableView.beginUpdates()

            tableView.insertRows(at: insertions.map { IndexPath(row: $0, section: 0) }, with: .automatic)

            tableView.deleteRows(at: deletions.map { IndexPath(row: $0, section: 0) }, with: .automatic)
            tableView.reloadRows(at: modifications.map { IndexPath(row: $0, section: 0) }, with: .automatic)
            tableView.endUpdates()
            break
        case .error(let error):
            print("Error: \(error)")
            break
        }
    }
}

如果在初始化通知后更新结果，我如何使用领域通知？

1 个答案: