小编Paa*_*une的帖子

我试图在第一次加载应用程序时执行segue.我可以在调试器中看到我的打印消息,但Perform Segue不起作用.我没有得到任何错误.有人可以告诉我什么错了吗？

import UIKit
import LocalAuthentication
let isFirstLaunch = UserDefaults.isFirstLaunch()
extension UserDefaults {
    // check for is first launch - only true on first invocation after app install, false on all further invocations
    // Note: Store this value in AppDelegate if you have multiple places where you are checking for this flag
    static func isFirstLaunch() -> Bool {
        let hasBeenLaunchedBeforeFlag = "hasBeenLaunchedBeforeFlag"
        let isFirstLaunch = !UserDefaults.standard.bool(forKey: hasBeenLaunchedBeforeFlag)
        if (isFirstLaunch) {

            UserDefaults.standard.set(true, forKey: hasBeenLaunchedBeforeFlag)
            UserDefaults.standard.synchronize()
        }
        return isFirstLaunch
    }
}

class …

我想Double在 Swift 中显示一个没有小数的。

在location.speed来自地图包。这是我尝试过的：

let kmt = location.speed * (18/5)
let theKmt = Double(round(10*kmt)/10)

statusLabel.text = "km/t\(theKmt)"