swift - 如何为 NSPersistentContainer 和 NSPersistentCloudKitContainer 创建同名但根据版本设置的变量？

Question

我无法将令人兴奋的核心数据堆栈更改为 NSPersistentCloudKitContainer，因为这只是 iOS 13 及更高版本的支持功能，但我希望为 iOS 13 及更高版本设置该设置，同时为早期版本设置 NSPersistentContainer。

我在使用 swift 和 iOS 方面有相当多的经验，但从来没有为版本控制和某些变量做这样的事情。

这是我在使用 iOS 13 之前的正常操作:

lazy var persistentContainer: NSPersistentContainer = {
    /*
     The persistent container for the application. This implementation
     creates and returns a container, having loaded the store for the
     application to it. This property is optional since there are legitimate
     error conditions that could cause the creation of the store to fail.
    */
    let container = NSPersistentContainer(name: "Shopping_App")
    container.loadPersistentStores(completionHandler: { (storeDescription, error) in
        if let error = error as NSError? {
            // Replace this implementation with code to handle the error appropriately.
            // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.

            /*
             Typical reasons for an error here include:
             * The parent directory does not exist, cannot be created, or disallows writing.
             * The persistent store is not accessible, due to permissions or data protection when the device is locked.
             * The device is out of space.
             * The store could not be migrated to the current model version.
             Check the error message to determine what the actual problem was.
             */
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
    })
    return container
}()

这是我想在 iOS 13 或更高版本的任何设备上使用的代码，但仍然使用 iOS 12 及更早版本的第一位代码。

lazy var persistentContainer: NSPersistentCloudKitContainer = {

    let container = NSPersistentCloudKitContainer(name: "Shopping_App")
    container.loadPersistentStores(completionHandler: {
        (storeDescription, error) in
        if let error = error as NSError? {
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
    })
    return container
}()

如果可能的话，我希望两个版本有相同的变量而不重新声明错误，如果这可能的话，如果那不可能的话，我想要一个解决方案，它不需要完全重写我所有的存储和检索核心数据、数据。

Answer 1

我找到了答案，结果非常简单。在这里:

lazy var persistentContainer: NSPersistentContainer = {  
    if #available(iOS 13.0, *) {  
        let container = NSPersistentCloudKitContainer(name: "Shopping_App")  
        container.loadPersistentStores(completionHandler: {  
            (storeDescription, error) in  
            if let error = error as NSError? {  
                fatalError("Unresolved error \(error), \(error.userInfo)")  
            }  
        })  
        return container  
    } else {  
        let container = NSPersistentContainer(name: "Shopping_App")  
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in  
            if let error = error as NSError? {  

                fatalError("Unresolved error \(error), \(error.userInfo)")  
            }  
        })  
        return container  
    }  
}()