xcode showViewController 不工作
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showViewController Not Working
提问by John Doe
I am developing an app in SWIFT and I am using the following code to show a view controller on a button click.
我正在 SWIFT 中开发一个应用程序，我正在使用以下代码在单击按钮时显示视图控制器。
let storyboard = UIStoryboard(name: "Main", bundle: nil);
var viewName:NSString = "websiteView"
let vc = storyboard.instantiateViewControllerWithIdentifier(viewName) as WebsiteViewController
self.showViewController(vc, sender: self)
it works perfectly when I test it for ios 8 but on ios 7 no matter what I do I get the following error message. I read on a forum that self.showViewController was only available for ios 8 but the compiler doesn't throw an error, does anyone know if I can use it?
当我为 ios 8 测试它时，它运行良好，但在 ios 7 上，无论我做什么，我都会收到以下错误消息。我在论坛上读到 self.showViewController 仅适用于 ios 8 但编译器不会抛出错误，有人知道我是否可以使用它吗？
showViewController:sender:]: unrecognized selector sent to instance 0x7f9552e7cc50
2014-11-15 09:25:49.565 Throw[80595:613] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[Throw.test showViewController:sender:]: unrecognized selector sent to instance 0x7f9552e7cc50'
2014-11-15 09:25:49.565 Throw[80595:613] *** 由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因：“-[Throw.test showViewController:sender:]：无法识别的选择器发送到实例 0x7f95052e
回答by Acey
The compiler didn't throw an error because you have the iOS 8.0 (or 8.1) SDK selected. That method is indeed iOS 8.0+ only. You can choose to use it if you call it conditionally, like so:
编译器没有抛出错误，因为您选择了 iOS 8.0（或 8.1）SDK。该方法确实仅适用于 iOS 8.0+。如果您有条件地调用它，您可以选择使用它，如下所示：
if (self.respondsToSelector(Selector("showViewController"))) {
self.showViewController(vc, sender: self)
} else {
//An example of the alternate if you are using navigation controller
self.navigationController?.pushViewController(vc, animated: true)
}
回答by f0go
You can use:
您可以使用：
self.navigationController?.pushViewController(vc as WebsiteViewController, animated: true)
which is compatible with iOS 7 and iOS 8
与 iOS 7 和 iOS 8 兼容
回答by kaushal
Update - A better and recommended way from swift2 for API version compatibility check
更新 - 来自 swift2 的更好和推荐的 API 版本兼容性检查方法
if #available(iOS 8, *) {
self.showViewController(vc, sender: self)
} else {
self.navigationController?.pushViewController(vc, animated: true)
}
Bonus : Use the @available attribute to decorate individual functions or entire classes this will give compile time version check for your own API
奖励：使用@available 属性来装饰单个函数或整个类，这将为您自己的 API 提供编译时版本检查
@available(iOS 8, *)
func compatibalityCheckForiOS8() -> Void { }
