iOS - Is saving to UserDefaults synchronous?

问题

Are operations on UserDefaults synchronous? For example does the second save wait for the first save to finish?

UserDefaults.standard.set(myValue1, forKey: "myValue1")
UserDefaults.standard.set(myValue2, forKey: "myValue2")

回答1:

From apple's documentation:

At runtime, you use UserDefaults objects to read the defaults that your app uses from a user’s defaults database. UserDefaults caches the information to avoid having to open the user’s defaults database each time you need a default value. When you set a default value, it’s changed synchronously within your process, and asynchronously to persistent storage and other processes.

来源：https://stackoverflow.com/questions/50206997/ios-is-saving-to-userdefaults-synchronous