sorting - 为什么会出现警告 : "Constant inferred to have type (), which may be unexpected"?

Question

我正在尝试对类的实例化项目数组进行排序:“Employees”。

但是我在 Playground 上遇到以下错误:

这是在我的 Playground 中编写的代码:

class Employee {
    var firstName:String = ""
    var lastName:String = ""
    init(fName:String, lName:String) {
        self.firstName = fName
        self.lastName = lName
    }
}

var employees = [Employee]()

// 1)
var employee = Employee(fName: "Ric", lName: "Lee")
employees.append(employee)

// 2)
employee = Employee(fName: "Ralph", lName: "Knott")
employees.append(employee)

// 3)
employee = Employee(fName: "Joe", lName: "Smirf")
employees.append(employee)

// 4)
employee = Employee(fName: "Meredith", lName: "Lind")
employees.append(employee)

// 5)
employee = Employee(fName: "Aarnald", lName: "Zingerhost")
employees.append(employee)

let sortedEmployees = employees.sort { (e1:Employee, e2:Employee) -> Bool in
    e1.lastName < e2.lastName
}

我在这里缺少什么？
为什么会出现警告？

Answer 1

原因是您使用了错误的函数(以前的sortInPlace):

在Swift 3中

• sort() 已重命名为 sorted()
• sortInPlace() 已重命名为 sort()

所以是

let sortedEmployees = employees.sorted { (e1:Employee, e2:Employee) -> Bool in
    e1.lastName < e2.lastName
}

来源:Swift Evolution: Apply API Guidelines to the Standard Library