非标称类型X不支持显式初始化

Question

我试图理解我在swift中对泛型做错了什么.

我创建了这个示例游乐场

import UIKit

public protocol MainControllerToModelInterface : class {
    func addGoal()
    init()
}

public protocol MainViewControllerInterface : class {
    associatedtype MODELVIEW
    var modelView: MODELVIEW? {get set}

    init(modelView: MODELVIEW)
}

public class MainViewController<M> : UIViewController, MainViewControllerInterface where M : MainControllerToModelInterface {
    public weak var modelView: M?

    required public init(modelView: M) {
        self.modelView = modelView
        super.init(nibName: String(describing: MainViewController.self), bundle: Bundle.main)
    }

    required public init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

public class Other<C, M> : NSObject where C : MainViewControllerInterface, C : UIViewController, M : MainControllerToModelInterface, C.MODELVIEW == M {
    var c : C?

    override init() {
        let m = M()
        self.c = C(modelView: m)
        super.init()
    }
}

这条线self.c = C(modelView: m)给了我这个错误non-nominal type 'C' does not support explicit initialization

从这个其他堆栈溢出问题我看到旧版Xcode版本中的这个错误意味着

cannot invoke initializer for type '%type' with an argument list of type '...' expected an argument list of type '...'

但是在操场上方,编译器缺少什么？

我在swift4/xcode9上.

更新

按照建议后Use C.init(modelView: m) rather than C(modelView: m),错误会发生变化:

No 'C.Type.init' candidates produce the expected contextual result type '_?'

比@ vini-app建议删除UIViewController以使其工作.我仍然不明白为什么当UIViewController存在时编译器不满意.知道C有那种有效的init方法还不够吗？

Answer 1

只需init在初始化泛型参数而不是"真实"类型时,只需显式使用:

self.c = C.init(modelView: m)