ios - TableView 不符合协议(protocol)

Question

我已经设置了一个基本的 CellAssociation 协议(protocol)。

但是，我添加到协议(protocol)中的任何内容都会:

"Type 'FooTableView' does not conform to protocol 'Cell Association'"

Xcode 似乎给了我一些提示:

"Multiple maching functions named 'register(cellClass:forCellReuseIdentifier:)' with type '(AnyClass?, String) -> ()' (aka '(Optional<AnyObject.Type>, String) -> ()')"

和..

"Rename to 'register(cellClass:forCellReuseIdentifier:)' to satisfy this requirement"

但是，看起来我的注册函数就是这样命名的。

这是 CellAssociation (TableView.swift)

import UIKit

protocol CellAssociation {
    associatedtype Cell: UITableViewCell

    func register()
    func register(cellClass: AnyClass?, forCellReuseIdentifier: String)

    func dequeueReusableCell(for: IndexPath) -> Cell
    func dequeueReusableCell(withIdentifier: String, for: IndexPath) -> UITableViewCell
}

extension CellAssociation {

    func register() {
        register(cellClass: Cell.self, forCellReuseIdentifier: String(describing: Cell.self))
    }

    func dequeueReusableCell(for indexPath: IndexPath) -> Cell {
        return dequeueReusableCell(withIdentifier: String(describing: Cell.self), for: indexPath) as! Cell
    }
}

这是一个试图遵守协议(protocol)的 TableView:

import UIKit

class LineupDraftSortMenuTableView: UITableView, CellAssociation {

    typealias Cell = LineupDraftSortMenuCell

    init() {
        super.init(frame: CGRect.zero, style: .plain)
        setup()
    }

    required convenience init?(coder: NSCoder) {
        self.init()
    }

    func setup() {
        rowHeight = 40
        separatorStyle = .none
        backgroundColor = UIColor.clear
        register()
    }
}

这个类会抛出一个错误:

"Type 'LineupDraftSortMenuTableView' does not conform to protocol 'CellAssociation'"

和 LineupDraftSortMenuCell

import UIKit

class LineupDraftSortMenuCell: UITableViewCell {

    let optionLabel = DraftboardLabel()
    let iconCheck = UIImageView()

    let borderView = UIView()

    var selectedOption: Bool = false { didSet { toggleIconCheck() } }

    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        setup()
    }

    required convenience init?(coder: NSCoder) {
        self.init()
    }

    func setup() {
        addSubviews()
        setupSubviews()
        addConstraints()
    }

    func addSubviews() {
        contentView.addSubview(optionLabel)
        contentView.addSubview(iconCheck)
        contentView.addSubview(borderView)
    }

    func setupSubviews() {
        backgroundColor = UIColor.clear
        contentView.backgroundColor = UIColor.clear
        selectionStyle = .none

        optionLabel.font = UIFont.openSans(weight: .Semibold, size: 9)
        optionLabel.textColor = UIColor.white
        optionLabel.letterSpacing = 0.5

        iconCheck.image = UIImage(named: "icon-check")
        iconCheck.contentMode = .scaleAspectFit
        iconCheck.isHidden = !selectedOption

        borderView.backgroundColor = UIColor(0x5c656f)
    }

    func addConstraints() {
        let viewConstraints: [NSLayoutConstraint] = [
            optionLabel.leftRancor.constraintEqualToRancor(rancor: contentView.leftRancor, constant: 20),
            optionLabel.centerYRancor.constraintEqualToRancor(rancor: contentView.centerYRancor),
            iconCheck.widthRancor.constraintEqualToConstant(constant: 12),
            iconCheck.heightRancor.constraintEqualToConstant(constant: 10),
            iconCheck.centerYRancor.constraintEqualToRancor(rancor: contentView.centerYRancor),
            iconCheck.rightRancor.constraintEqualToRancor(rancor: contentView.rightRancor, constant: -20),
            borderView.leftRancor.constraintEqualToRancor(rancor: contentView.leftRancor, constant: 10),
            borderView.rightRancor.constraintEqualToRancor(rancor: contentView.rightRancor, constant: -10),
            borderView.bottomRancor.constraintEqualToRancor(rancor: contentView.bottomRancor),
            borderView.heightRancor.constraintEqualToConstant(constant: 1),
        ]

        optionLabel.translatesAutoresizingMaskIntoConstraints = false
        iconCheck.translatesAutoresizingMaskIntoConstraints = false
        borderView.translatesAutoresizingMaskIntoConstraints = false

        NSLayoutConstraint.activate(viewConstraints)
    }

    func toggleIconCheck() {
        iconCheck.isHidden = !selectedOption
    }
}

Answer 1

你的协议(protocol)有这样的要求:

protocol CellAssociation {
    func register(cellClass: AnyClass?, forCellReuseIdentifier: String)
}

但是您的 TableView 子类 LineupDraftSortMenuTableView 从未实现该方法。所以不符合协议(protocol)。

也许您假设该函数声明与 UITableView 已经实现的内容相匹配，因此 UITableView 子类可以符合您的协议(protocol)而无需显式实现它。但事实并非如此。 UITableView 已有的方法是:

func register(_ cellClass: AnyClass?, forCellReuseIdentifier identifier: String)

下划线有很大的不同!

因此，如果您重写协议(protocol)及其扩展以匹配 UITableView 已经实现的内容，您的代码将编译，如下所示:

protocol CellAssociation {
    associatedtype Cell: UITableViewCell
    func register()
    func register(_ cellClass: AnyClass?, forCellReuseIdentifier: String)
    func dequeueReusableCell(for: IndexPath) -> Cell
    func dequeueReusableCell(withIdentifier: String, for: IndexPath) -> UITableViewCell
}

extension CellAssociation {
    func register() {
        register(Cell.self, forCellReuseIdentifier: String(describing: Cell.self))
    }
    func dequeueReusableCell(for indexPath: IndexPath) -> Cell {
        return dequeueReusableCell(withIdentifier: String(describing: Cell.self), for: indexPath) as! Cell
    }
}

一旦你说了，就可以合法地说:

class LineupDraftSortMenuTableView: UITableView, CellAssociation {
    // ...
}