iOS领域结果<object>无法添加结果<project>

时间:2017-04-29 12:07:09

标签: ios swift3 realm

我尝试为realm结果创建通用的UITableView dataSource类,但是当我尝试发送不同的realmResults时 结果片剂;&LT;&GT;对象&LT;&GT;&GT;在示例结果上我收到此错误消息:

  

无法转换类型&#39;结果&#39;&#39;项目&#39;&gt;&#39;预期的元素类型&#39;结果&#39;对象&#39;&#39;

class RealmResultsTableViewDataSource: TableViewDataSource {

var realmResults:[Results<Object>]
var notificationTokens: [NotificationToken] = []

init(tableView: UITableView, realmResults: [Results<Object>], configCell: @escaping TableViewConfigCellBlock, canEdit: TableViewCanEditCellBlock?, canMove: TableViewCanMoveRowBlock?, commitEditing: TableViewCommitEditingStyleBlock?) {

    self.realmResults = realmResults

    super.init(tableView: tableView, dataSource: [], configCell: configCell, canEdit: canEdit, canMove: canMove, commitEditing: commitEditing)

    addTokens(for: realmResults)
}

deinit {
    for token in notificationTokens {
        token.stop()
    }
}

override var sections: Int{
    get { return realmResults.count }
}

override func numberOfRows(section: Int) -> Int {
    return realmResults[section].count
}

// MARK: Add tokens

func addTokens(for results: [Results<Object>]) {
    for result in results {

       let notificationToken = result.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
                fatalError("\(error)")
                break
            }
        }

        notificationTokens.append(notificationToken)
    }
}

override func dataSourceObject(on indexPath: IndexPath) -> Any {

    return realmResults[indexPath.section][indexPath.row]
}

}

让领域=试试!境界()

    let result = realm.objects(Project.self).filter("id < 10").sorted(byKeyPath: "id", ascending: true)

    tableViewDataSource = RealmResultsTableViewDataSource(tableView: tableView, realmResults: [result], configCell: { (tableView, indexPath, object) -> UITableViewCell in

        let cell = tableView.dequeueReusableCell(withIdentifier:ProjectListTableViewCell.cellIdentifier , for: indexPath)

        return cell

    }, canEdit: nil, canMove: nil, commitEditing: nil)



import RealmSwift

class Project: Object {

    dynamic var id: Int = 0
    dynamic var name: String = ""
}

解决方案:

class RealmResultsTableViewDataSource<T: Object>: TableViewDataSource {

    var realmResults:Results<T>
    var notificationTokens: [NotificationToken] = []


    init(tableView: UITableView, realmResults: Results<T>, configCell: @escaping TableViewConfigCellBlock, canEdit: TableViewCanEditCellBlock?, canMove: TableViewCanMoveRowBlock?, commitEditing: TableViewCommitEditingStyleBlock?) {

        self.realmResults = realmResults

        super.init(tableView: tableView, dataSource: [], configCell: configCell, canEdit: canEdit, canMove: canMove, commitEditing: commitEditing)


        addTokens(for: self.realmResults)
    }

    deinit {

        for token in notificationTokens {
            token.stop()
        }
    }

    override var sections: Int{

        get{
          return 1
        }
    }

    override func numberOfRows(section: Int) -> Int {
        return realmResults.count
    }


    // MARK: Add tokens

    func addTokens(for results: Results<T>) {

           let notificationToken = results.addNotificationBlock { [weak self] (changes: RealmCollectionChange) in
                guard let tableView = self?.tableView else { return }
                guard tableView.dataSource === self 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
                    fatalError("\(error)")
                    break
                }
            }

            notificationTokens.append(notificationToken)
    }

    override func dataSourceObject(on indexPath: IndexPath) -> Any {

        return realmResults[indexPath.row]
    }

    override func removeObject(indexPath: IndexPath) {
       // assertionFailure("you can use ramoveObject int \(String(describing: self))")
    }

}

1 个答案:

答案 0 :(得分:1)

AFAIK,Realm Swift还不支持多态性。

  

目前的解决方案是使用组合而不是继承。   关于它有很多好的论据(Gang of Four和Joshua   布洛赫提到了这种方法的一些着名支持者。)

     

另一方面,我们正考虑允许继承,但它   不允许查询。例如:动物由两个延伸   狗,猫和鸭。您将无法使用for查询Animals   腿和所有的狗和猫,但不是鸭子。我们觉得这会是   这是一种非常严重的行为,但却渴望倾听更多意见。

这里讨论(这里讨论产品的java版本,所以它只是你的起点......):https://github.com/realm/realm-java/issues/761

最简单的解决方案[但如果你需要将这些方法与Object的其他子类重用]可能不是最好的解决方案 带有“项目”的“对象”