Question

我在尝试时崩溃了：

static func getDeviceUUID() -> String {
        guard let uuid = UIDevice.current.identifierForVendor?.uuidString else {
            assertionFailure("Nil while unwrapping UIDevice.current.identifierForVendor?.uuidString")
            return ""}
            return uuid
    }

错误说：Thread 9: Fatal error: Nil while unwrapping UIDevice.current.identifierForVendor?.uuidString

但是当我尝试在控制台中记录它时，它说：

 po UIDevice.current.identifierForVendor?.uuidString
▿ Optional<String>
  - some : "39DEFA50-D6A1-4788-BCCC-5E2A28A04C57"

所以，它实际上有价值。为什么会发生崩溃？

Answer 1

工作正常

         let frame:CGRect = CGRect(x: 0, y: 600, width: self.view.frame.width, height: self.view.frame.height/3)
         self.datePicker = CustomDatePicker.instanceFromNib(frame: frame) as? CustomDatePicker

        self.datePicker?.configureDatePicker()
        datePicker?.customPickerDelegate = self
        self.view.addSubview(self.datePicker!)
        UIView.animate(withDuration: 1.5, animations: {

            DILog.print(items: "Updated Y is \(self.view.frame.height - self.view.frame.height/3)")

            self.datePicker.frame = CGRect(x: 0, y: 300, width: self.view.frame.width, height: self.view.frame.height/3)

        }, completion: { (value) in

        })

Answer 2

尝试从AdSupport框架中获取IDFA时，我遇到了类似的问题：

ASIdentifierManager.shared().advertisingIdentifier.uuidString
// causes exception

在这种情况下，似乎Objective-C代码库中有一个标记错误的'nonnull'方法，由于UUID类的uuidString方法返回的是值类型（字符串），因此无法解决。在Obj-C中，它将返回引用类型（NSString）： https://forums.swift.org/t/is-it-safe-to-cast-a-nonnull-objc-type-to-a-swift-optional/10658

由于这两个都使用了UUID类，所以我猜这是同样的问题。

上面的链接建议的解决方法是构建一个Obj-C包装器来访问UUID：

+ (nullable NSString*)getUUIDFromDevice {
    NSString *uuid = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
    if (uuid) {
        return uuid;
    } else {
        return nil;
    }
}

不幸的是，这很难测试，因为不清楚UUID值何时确切为零。

Answer 3

也许是因为你没有检查用户是否允许检查它。

guard ASIdentifierManager.shared().isAdvertisingTrackingEnabled else {
    return nil
}          
return ASIdentifierManager.shared().advertisingIdentifier.uuidString

顺便说一句，对于 iOS14+，您应该进行不同的检查：

import AdSupport
import AppTrackingTransparency

extension ASIdentifierManager {
    //NOTE: if the user has enabled Limit Ad Tracking, this IDFA will be all zeros on a physical device
    static var identifierForAdvertising: String {
        if #available(iOS 14, *) {
            guard ATTrackingManager.trackingAuthorizationStatus == .authorized else {
                return ""
            }
        } else {
            guard ASIdentifierManager.shared().isAdvertisingTrackingEnabled else {
                return ""
            }
        }
        return ASIdentifierManager.shared().advertisingIdentifier.uuidString
    }
}

尝试获取UIDevice.current.identifierForVendor？.uuidString时崩溃

3 个答案: