Swift2 ViewController不符合协议'；jAppleClendarViewDataSource'；

我正在使用Swift 2和JTAppleCalendar Cocoa Pod在我的应用程序中构建日历

我正在尝试实现函数

configureCalendar

，这是协议

JTAppleCalendarViewDataSource

中唯一的函数

这是pod给出的功能定义：

func configureCalendar(calendar: JTAppleCalendarView) -> (startDate: NSDate, endDate: NSDate, numberOfRows: Int, calendar: NSCalendar)

这是我的实现：

extension CalendarViewController:  JTAppleCalendarViewDataSource {
    func configureCalendar(calendar: JTAppleCalendarView) -> (startDate: NSDate, endDate: NSDate, numberOfRows: Int, calendar: NSCalendar) {
        formatter.dateFormat = "yyyy MM dd"
        formatter.timeZone = NSCalendar.currentCalendar().timeZone
        formatter.locale = NSCalendar.currentCalendar().locale
        let startDate = formatter.dateFromString("2017 01 01")
        let endDate = formatter.dateFromString("2017 12 31")
        let calendar = NSCalendar.currentCalendar()
        return (startDate!, endDate!, 5, calendar)
    }    
}

我从编译器中获得此错误：

CalendarViewController.swift:32:1: Type 'CalendarViewController' does not conform to protocol 'JTAppleCalendarViewDataSource'

JTAppleCalendar.JTAppleCalendarViewDataSource:11:17: Protocol requires function 'configureCalendar' with type '(JTAppleCalendarView) -> (startDate: NSDate, endDate: NSDate, numberOfRows: Int, calendar: NSCalendar)'

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为什么我不遵守协议

将我的return语句更改为如下所示：

return (startDate: startDate!, endDate: endDate!, numberOfRows: 5, calendar: calendar)