👝 💞 📌 我们如何提出TableAdapter并简化UITableView的工作 📐 🙇 ⛓️

在工作时，UITableView我想避免编写模板代码，如果您需要动态更新表的状态，则模板代码会更加复杂。Apple在WWDC 2019上展示了针对此问题的解决方案，但它仅适用于iOS13。作为移动应用程序开发工作室，我们没有选择最低版本的iOS的奢望。

因此，我们实现了以数据驱动的方式处理表的愿景，同时简化了沿途单元的配置。并且他们添加了一个动画表更新，该更新基于自动计算线性时间O（n）的新旧数据之间的差异。所有这些我们都设计到一个名为TableAdapter的小型库中。

我们将在本文中讨论我们的工作以及如何做到这一点。

TableAdapter的优缺点

优点

动画表更新
自动线性时间差计算
无需继承表，单元格或模型
不再 dequeReusable...
类型安全的单元设置，页眉/页脚
以任何方式初始化单元
容易的部分设置
易于扩展

缺点

, Hashable. , - Swift, .. . - .

– :

1. , /

1.1

, , Hashable.

extension User: Hashable { ... }

1.2

Configurable, . , .

extension Cell: Configurable {

    public func setup(with item: User) {
        textLabel?.text = item.name
    }
}

, , , . , setup(with:) .

1.3 /

/ Configurable, . / 1.3 .

2.

() , /. Section<Item, SectionId>, (Item) (SectionId). (id) Hashable, .

/

/ header/footer.

/

/ headerIdentifier/footerIdentifier, . , Configurable ( 1.3).

let section = Section<User, Int>(
    id: 0,
    items: users,
    header: "Users Section",
    footer: "Users Section",
    headerIdentifier: "HeaderReuseIdentifier",
    footerIdentifier: "FooterReuseIdentifier"
)

id .

3.

TableAdapter<Item, SectionId>, (Item) (SectionId). , .

CellReuseIdentifierProvider, . , IndexPath , .

ellDidSelectHandler, , IndexPath .

lazy var adapter = TableAdapter<User, Int>(
    tableView: tableView,
    cellIdentifierProvider: { (indexPath, item) -> String? in
        // Return cell reuse identifier for item at indexPath
    },
    cellDidSelectHandler: { [weak self] (table, indexPath, item) in
        // Handle cell selection for item at indexPath
    }
)

adapter.update(with: [section], animated: true)

class ViewController: UIViewController {

    let tableView = ...

    lazy var adapter = TableAdapter<User, Int>(
        tableView: tableView,
        cellIdentifierProvider: { (indexPath, item) -> String? in
            return "CellReuseIdentifier"
        },
        cellDidSelectHandler: { [weak self] (table, indexPath, item) in
            // Handle cell selection for item at indexPath
        }
    )

    let users: [User] = [...]

    override func viewDidLoad() {
        super.viewDidLoad()

        setupTable()

        let section = Section<User, Int>(
            id: 0,
            items: users,
            header: "Users Section",
            footer: "Users Section",
            headerIdentifier: "HeaderReuseIdentifier",
            footerIdentifier: "FooterReuseIdentifier"
        )

        adapter.update(with: [section]], animated: true)
    }

    func setupTable() {
        tableView.register(
            Cell.self,
            forCellReuseIdentifier: "CellReuseIdentifier"
        )

        tableView.register(
            Header.self,
            forHeaderFooterViewReuseIdentifier identifier: "HeaderReuseIdentifier"
        )
        tableView.register(
            Footer.self,
            forHeaderFooterViewReuseIdentifier identifier: "FooterReuseIdentifier"
        )
    }
}

Hashable , (associated value).

, CellReuserIdentifierProvider. A , "Cell" :

tableView.register(
    Cell.self,
    forCellReuseIdentifier: adapter.defaultCellIdentifier
)

/

headerIdentifier/footerIdentifier . / , "Header"/"Footer".

tableView.register(
    HeaderView.self,
    forHeaderFooterViewReuseIdentifier identifier: adapter.defaultHeaderIdentifier
)
tableView.register(
    FooterView.self,
    forHeaderFooterViewReuseIdentifier identifier: adapter.defaultFooterIdentifier
)

Sender

, , , , TableAdapter'a sender. , / SenderConfigurable.


class ViewController: UIViewController {

    lazy var adapter = TableAdapter<User, Int>(
        tableView: tableView,
        sender: self
    )
}

extension Cell: SenderConfigurable {

    func setup(with item: User, sender: ViewController) {
        textLabel?.text = item.name
        delegate = sender
    }
}

: , . , setup(with:sender:) .

, CellProvider, :

lazy var adapter = TableAdapter<User, Int>(
    tableView: tableView,
    cellProvider: { (table, indexPath, user) in
        let cell = table.dequeueReusableCell(
            withIdentifier: "CellReuseIdentifier",
            for: indexPath
        ) as! Cell

        cell.setup(with: user)

        return cell
    }
)

/ TableAdapter .

(diff) , . , A technique for isolating differences between files. O(n) . Hashable.

, , performBatchUpdates(_:completion:) . . .

() (id). .

let sectionsDiff = try calculateDiff(form: oldSections, to: newSections)

, , . , , id. , , , . , , .

let intermediateSections = applyDiff(sectionsDiff, to: oldSections)

( id) . . , , .

let rowsDiff = try calculateRowsDiff(from: intermediateSections, to: newSections)

let diff = Diff(
    sections: sectionsDiff,
    rows: rowsDiff,
    intermediateData: intermediateSections,
    resultData: newSections
)

: ( ) , .

data = diff.intermediateData

tableView.insertSections(diff.sections.inserts, with: animationType)
tableView.deleteSections(diff.sections.deletes, with: animationType)
diff.sections.moves.forEach { tableView.moveSection($0.from, toSection: $0.to) }

: () , .

data = diff.resultData

tableView.deleteRows(at: diff.rows.deletes, with: animationType)
tableView.insertRows(at: diff.rows.inserts, with: animationType)
diff.rows.moves.forEach { tableView.moveRow(at: $0.from, to: $0.to) }

1: . «» «» .

2: , .. . , , , , . .. , . adapter.update(with: sections, animated: false) .

`Configurable`

, :

let user = users[indexPath.row]

let cell = tableView.dequeueReusableCell(
    withIdentifier: cellId,
    for: indexPath
) as! Cell

cell.setup(with: user)

. (associatedtype).

Configurable, :

protocol Configurable {

    associatedtype ItemType: Any
    func setup(with item: ItemType)
}

, dequeueReusableCell(withIdentifier:for:) Configurable - ItemType. AnyConfigurable:

protocol AnyConfigurable {

    func anySetup(with item: Any)
}

, :

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

if let cell = cell as? AnyConfigurable {
    cell.anySetup(with: item)
}

Configurable AnyConfigurable :

extension Configurable {

    func anySetup(with item: Any) {
        if let item = item as? ItemType {
            setup(with: item)
        }
    }
}

, - «» , . , .

, Swift type-erased wrappers. AnyHashable, AnyIndex.

: . : .

GitHub

结果，我们得到了一个解决方案，可让您方便地配置单元，另外编写更少的模板代码和动画。同时，如有必要，仍然可能进行低级表设置和功能扩展。

GitHub实施

我们如何提出TableAdapter并简化UITableView的工作