xcode 非标称类型 X 不支持显式初始化
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/46458657/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
non-nominal type X does not support explicit initialization
提问by Luca Bartoletti
I'm trying to understand what I'm doing wrong with generics in swift.
我试图快速了解我在泛型方面做错了什么。
I created this sample playground
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()
}
}
the line self.c = C(modelView: m)gives me this error non-nominal type 'C' does not support explicit initialization
该行self.c = C(modelView: m)给了我这个错误non-nominal type 'C' does not support explicit initialization
From this other stack overflowquestion I see that this error in older Xcode versions means
从另一个堆栈溢出问题中，我看到旧 Xcode 版本中的此错误意味着
cannot invoke initializer for type '%type' with an argument list of type '...' expected an argument list of type '...'
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?
但是在上面的操场上，编译器缺少什么？
I'm on swift4/xcode9.
我在 swift4/xcode9 上。
Update
更新
After following the suggestion Use C.init(modelView: m) rather than C(modelView: m)the error changes in:
遵循建议后Use C.init(modelView: m) rather than C(modelView: m)，错误更改为：
No 'C.Type.init' candidates produce the expected contextual result type '_?'
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?
比@vini-app 建议删除 UIViewController 以使其正常工作。我仍然不明白为什么当 UIViewController 存在时编译器不高兴。知道 C 有那个有效的 init 方法还不够吗？
回答by andyvn22
You just need to use initexplicitly whenever you're initializing a generic parameter rather than a "real" type:
您只需要init在初始化泛型参数而不是“真实”类型时显式使用：
self.c = C.init(modelView: m)
回答by rounak
Use C.init(modelView: m)rather than C(modelView: m). That should fix it.
使用C.init(modelView: m)而不是C(modelView: m). 那应该解决它。
回答by Vini App
Please check :
请检查 ：
In your code you are doing like this C : MainViewControllerInterface, C : UIViewController.
在您的代码中，您正在这样做C : MainViewControllerInterface, C : UIViewController。
It is treating Cas ViewController, then there is no initin ViewController like init(modelView: M)thats why its throwing error
它被C视为 ViewController，然后init在 ViewController 中没有像init(modelView: M)这就是它抛出错误的原因
public class Other<C, M> : NSObject where C : MainViewControllerInterface, M : MainControllerToModelInterface, C.MODELVIEW == M {
var c : C?
override init() {
let m = M()
self.c = C(modelView: m)
super.init()
}
}
