ios - 在基类或扩展 Swift 的静态方法中获取派生类型的类型名称

Question

长话短说将其粘贴到 Swift playground 中:

import UIKit

public protocol NibLoadable {
    static var nibName: String { get }
}

extension NibLoadable where Self: UIView {
    public static var nibName: String {
        return String(describing: self)
    }

    func printName(){
        print(Self.nibName)
    }
}

public class Shoes: UIView, NibLoadable {


    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        printName()
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        printName()
    }
}

public class Cake: Shoes {

}

let cake = Cake() // this line prints 'Shoes'

如何让它打印Cake，而不是Shoes？

完整解释:

我找到了将 xib 文件加载到 Storyboard中的方法，如下所示: https://stackoverflow.com/a/47295926/2057955

这非常有效，但是我必须像这样将样板 NibLoadable 代码放入每个 View 中:

required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setupFromNib()
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        setupFromNib()
    }

当您以这种方式获得 20-30 次观看时，这显然很烦人。

所以我正在尝试设置一个基类来处理这个问题，然后让所有东西都继承它。

不幸的是，无论我尝试了什么，String(describing: Self.self) 总是返回我的基类的名称，而不是派生类的名称。

当我在 XCode 中打开 Storyboard 时，我在控制台日志中收到此异常:

[MT] IBSceneUpdate: [scene update, delegate=] Error Domain=IBMessageChannelErrorDomain Code=3 "Failed to communicate with helper tool" UserInfo={NSLocalizedFailureReason=The agent raised a "NSInternalInconsistencyException" exception: Could not load NIB in bundle: 'NSBundle (loaded)' with name 'BaseNibLoadable.Type', IBMessageSendChannelException=Could not load NIB in bundle: 'NSBundle (loaded)' with name 'BaseNibLoadable.Type', NSLocalizedDescription=Failed to communicate with helper tool}

例子:

@IBDesignable
class BaseNibLoadable: UIView, NibLoadable {
    // MARK: - NibLoadable
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setupFromNib()
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        setupFromNib()
    }
}

@IBDesignable
class SomeHeader: BaseNibLoadable {

    @IBOutlet fileprivate weak var headerLabel: UILabel!
    @IBInspectable var header: String? {
        didSet {
            self.headerLabel.text = header
        }
    }
}

显然，我的主包(两者的包相同)包含 SomeHeader.xib 文件。

所以我正在寻找的是以某种方式获取在 nibName 静态方法中实例化的实际类型的名称。

更新根据要求，这是我在问题顶部链接的原始答案(更确切地说，只是它的代码，否则它很长......请点击链接):

public protocol NibLoadable {
    static var nibName: String { get }
}

public extension NibLoadable where Self: UIView {

    public static var nibName: String {
        return String(describing: Self.self) // defaults to the name of the class implementing this protocol.
    }

    public static var nib: UINib {
        let bundle = Bundle(for: Self.self)
        return UINib(nibName: Self.nibName, bundle: bundle)
    }

    func setupFromNib() {
        guard let view = Self.nib.instantiate(withOwner: self, options: nil).first as? UIView else { fatalError("Error loading \(self) from nib") }
        addSubview(view)
        view.translatesAutoresizingMaskIntoConstraints = false
        view.leadingAnchor.constraint(equalTo: self.safeAreaLayoutGuide.leadingAnchor, constant: 0).isActive = true
        view.topAnchor.constraint(equalTo: self.safeAreaLayoutGuide.topAnchor, constant: 0).isActive = true
        view.trailingAnchor.constraint(equalTo: self.safeAreaLayoutGuide.trailingAnchor, constant: 0).isActive = true
        view.bottomAnchor.constraint(equalTo: self.safeAreaLayoutGuide.bottomAnchor, constant: 0).isActive = true
    }
}

更新 2

我确实知道子类此时肯定在堆栈中，因为如果我记录 Thread.callStackSymbols，实际的具体 View 类名称就在那里。

Answer 1

How do i make it print Cake, not Shoes?

改变

print(Self.nibName)

到

print(type(of:self).nibName)