我应该在swift的getter方法中返回什么

private var storedUserState: UserState
var userState: UserState {
    get {
        return storedUserState
    }
    set {
        print("Before: \(self.storedUserStatE)")
        storedUserState = newValue
        print("After: \(self.storedUserStatE)")
    }
}

如果您想自定义setter方法,但希望该属性保持存储,请使用属性观察器而不是覆盖访问器：

var userState: UserState = nil {
    willSet(newStatE) {
        print("About to set userState: \(newStatE)")
    }
    didSet {
        print("Finished: new=\(userStatE),old=\(oldvalue)")
    }
}