在Swift中返回instancetype

概述我试图做这个扩展： extension UIViewController{ class func initialize(storyboardName: String, storyboardId: String) -> Self { let storyboad = UIStoryboard(name: storyboardName, bundle: nil) 我试图做这个扩展：

extension UIVIEwController{    class func initialize(storyboardname: String,storyboardID: String) -> Self    {        let storyboad = UIStoryboard(name: storyboardname,bundle: nil)        let controller = storyboad.instantiateVIEwControllerWithIDentifIEr(storyboardID) as! Self        return controller    }}

但我得到编译错误：

error: cannot convert return Expression of type ‘UIVIEwController’ to
return type ‘Self’

可能吗？我也想做为init(storyboardname：String，storyboardID：String)

类似于 Using ‘self’ in class extension functions in Swift，您可以定义一个通用辅助方法，从调用上下文中推断self的类型：

extension UIVIEwController{    class func instantiateFromStoryboard(storyboardname: String,storyboardID: String) -> Self    {        return instantiateFromStoryboardHelper(storyboardname,storyboardID: storyboardID)    }    private class func instantiateFromStoryboardHelper<T>(storyboardname: String,storyboardID: String) -> T    {        let storyboard = UIStoryboard(name: storyboardname,bundle: nil)        let controller = storyboard.instantiateVIEwControllerWithIDentifIEr(storyboardID) as! T        return controller    }}

然后

let vc = MyVIEwController.instantiateFromStoryboard("name",storyboardID: "ID")

编译，类型推断为MyVIEwController。

Swift 3的更新：

extension UIVIEwController{    class func instantiateFromStoryboard(storyboardname: String,storyboardID: String) -> Self    {        return instantiateFromStoryboardHelper(storyboardname: storyboardname,bundle: nil)        let controller = storyboard.instantiateVIEwController(withIDentifIEr: storyboardID) as! T        return controller    }}

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