Ios Swift-从月、日、年组件获取日期

如何将DateComponents转换为日期对象。 目前，我有以下代码

Calendar.date(from: DateComponents(year: 2018, month: 1, day: 15))

但是我得到一个错误，指出“没有'date'候选者生成预期的上下文结果类型'date'

对于这个基本问题，我很抱歉，但是我仍然在努力解决如何在Swift中使用日期的问题。您不能在类型上调用

date（从
调用）。您必须使用日历的一个实例，或者是
当前的
日历

Calendar.current.date(from: DateComponents(year: 2018, month: 1, day: 15))

还是固定的

let calendar = Calendar(identifier: .gregorian)
calendar.date(from: DateComponents(year: 2018, month: 1, day: 15))

//create an instance of DateComponents to keep your code flexible
var dateComponents = DateComponents()

//create the date components
dateComponents.year = 2018
dateComponents.month = 1
dateComponents.day = 15
//dateComponents.timeZone = TimeZone(abbreviation: "EST")
dateComponents.hour = 4
dateComponents.minute = 12

//make something useful out of it
func makeACalendarObject(){

//create an instance of a Calendar for point of reference ex: myCalendar, and use the dateComponents as the parameter
let targetCalendar = Calendar.current
let newCalendarObject = targetCalendar.date(from: dateComponents)


guard let newCalObject = newCalendarObject else {
    return
}
print(newCalObject)
}
//call the object
makeACalendarObject()