So I'm a bit dismayed that Apple has replaced a transparent, easy-to-handle NSUInteger with an HKQueryAnchor but has not provided an easy way to persist that HKQueryAnchor. Has anyone found a good way to do this with NSUserDefaults? The only persistence method I have seen is an archiver to a local file, but my app persists everything in NSUserDefaults, and I'd like to keep it that way if possible. Is there a reliable way to store an HKQueryAnchor this way?

因此，苹果用HKQueryAnchor替换了透明、易于处理的NSUInteger，但没有提供一种简单的方法来保持HKQueryAnchor，这让我有点失望。有没有人找到了使用NSUserDefaults的好方法？我见过的唯一的持久化方法是本地文件的存档程序，但我的应用程序在NSUserDefaults中持久化所有内容，如果可能的话，我想保持这种方式。这样存储HKQueryAnchor有没有可靠的方法？

You can convert it to NSData using NSKeyedArchiver and store that in the user defaults.

您可以使用NSKeyedArchiver将其转换为NSData，并将其存储在用户默认设置中。

To store:

要存储：

NSData *data = [NSKeyedArchiver archivedDataWithRootObject:anchor];
[[NSUserDefaults standardUserDefaults] setObject:data forKey:@"AnchorData"];

To retrieve:

要检索，请执行以下操作：

NSData *data = [[NSUserDefaults standardUserDefaults] objectForKey:@"AnchorData"];
HKQueryAnchor *anchor = [NSKeyedUnarchiver unarchiveObjectWithData:data];

Swift 5

You can declare the anchor as a computed variable which decodes the Data that you store in NSUserDefaults using NSKeyedUnarchiver

您可以将锚点声明为计算变量，该变量使用NSKeyedUnasiver对存储在NSUserDefaults中的数据进行解码

@AppStorage("anchorKey") private var encodedAnchor: Data?
    private var myAnchor: HKQueryAnchor? {
        if let encodedAnchor {
            // Decode the data to get HKQueryAnchor
            if let decodedAnchor = try? NSKeyedUnarchiver.unarchivedObject(ofClass: HKQueryAnchor.self, from: encodedAnchor){
                return decodedAnchor
            }
        }
        return nil
    }

On your HKAnchoredObjectQuery, you can then encode the newAnchor which the closure provides using NSKeyedArchiver which stores it to your stored value using NSUserDefaults

在HKAnchoredObtQuery上，然后可以使用NSKeyedArchiver对闭包提供的新Anchor进行编码，后者使用NSUserDefaults将其存储到您的存储值中

if let newEncodedAnchor = try? NSKeyedArchiver.archivedData(withRootObject: newAnchor, requiringSecureCoding: true) {
          // Store the encoded anchor data in UserDefaults
          self.myAnchor = newEncodedAnchor
      }

This answer is building off @allmightu 's answer, but without the SwiftUI @AppStorage requirement. I also packaged it into a nice get/set syntax, so this is pretty much invisible to any consumer of the variable.

这个答案是在@allmightu的S答案的基础上构建的，但没有SwiftUI@AppStorage要求。我还将它打包到一个很好的Get/Set语法中，所以对于该变量的任何使用者来说，这几乎是不可见的。

    let anchorKey = "defaults-anchor-key"
    var anchor: HKQueryAnchor? {
        get {
            guard let anchorData = UserDefaults.standard.data(forKey: anchorKey) else {
                return nil
            }
            return try? NSKeyedUnarchiver.unarchivedObject(ofClass: HKQueryAnchor.self, from: anchorData)
        }
        set {
            guard let newValue = newValue else {
                UserDefaults.standard.set(nil, forKey: anchorKey)
                return
            }
            if let anchorData = try? NSKeyedArchiver.archivedData(withRootObject: newValue, requiringSecureCoding: true) {
                UserDefaults.standard.set(anchorData, forKey: anchorKey)
            }
        }
    }