非名义类型X不支持显式初始化 [英] non-nominal type X does not support explicit initialization

问题描述

我创建了这个示例游乐场

  import UIKit 
 
公共协议MainControllerToModelInterface：class {
 func addGoal（）
 init（）
} 
 
公共协议MainViewControllerInterface：class {
 associatedtype MODELVIEW 
 var modelView：MODELVIEW？ {get set} 
 
 init（modelView：MODELVIEW）
} 
 
 public class MainViewController< M> ：UIViewController，MainViewControllerInterface其中M：MainControllerToModelInterface {
 public weak var modelView：M？ 
 
需要public init（modelView：M）{
 self.modelView = modelView 
 super.init（nibName：String（描述：MainViewController.self），bundle：Bundle.main ）
 
 
需要public init？（coder aDecoder：NSCoder）{
 fatalError（init（coder :) has been implemented now）
} 
} 
 
公开课其他< C，M> ：NSObject其中C：MainViewControllerInterface，C：UIViewController，M：MainControllerToModelInterface，C.MODELVIEW == M {
 var c：C？ 
 
覆盖init（）{
 let m = M（）
 self.c = C（modelView：m）
 super.init（）
 } 
 
  

行 self.c = C（modelView ：m）给我这个错误非名义类型'C'不支持显式初始化

从这个其他堆栈溢出问题我发现旧版Xcode版本中的这个错误意味着
$ b $ p $ 不能用类型''的参数列表调用类型'％type'的初始值设定项。 ..'期望的类型为'...'的参数列表

但是在操作上面什么是编译器缺失？

我在swift4 / xcode9上。

更新 b

遵循建议使用C.init（modelView：m）而不是C（modelView：m）错误更改：

否'C.Type.init'候选产生预期的上下文结果类型'_？'

比@ vini-app建议移除UIViewController以使其工作。我仍然不明白为什么当UIViewController存在时编译器不开心。是否仅仅知道C有这个有效的init方法是不够的？

解决方案

您只需要使用

 自己初始化一个泛型参数时显式初始化 .c = C.init（modelView：m）
  

I'm trying to understand what I'm doing wrong with generics in swift.

I created this sample playground

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()
    }
}

the line self.c = C(modelView: m) gives me this error non-nominal type 'C' does not support explicit initialization

From this other stack overflow question I see that this error in older Xcode versions means

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

But in the playground above what is the compiler missing?

I'm on swift4/xcode9.

Update

After following the suggestion Use C.init(modelView: m) rather than C(modelView: m) the error changes in:

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

Than @vini-app suggested to remove the UIViewController to make it works. By I still don't understand why the compiler is not happy when UIViewController is there. Is it not enough to know that C has that valid init method?

解决方案

You just need to use init explicitly whenever you're initializing a generic parameter rather than a "real" type:

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

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