Swift NSDateComponents仅在某些日子每天复发

Question

我试图为HomeKit创建一个可以反复触发的HMTimerTrigger。我开始使用一个系统，用户可以决定每周，每天等等，但现在已经决定切换到一个系统，用户只指定一周中的某些日期（例如星期一和星期五等）。这是我的代码的当前状态：

let calendar = NSCalendar.currentCalendar()
    let selectedDate = self.selectedDate
    let dateComp = calendar.components([NSCalendarUnit.Second, .Minute, .Hour, .Day, .Month, .Year, .Era] , fromDate: selectedDate)
    let fireDate = calendar.dateWithEra(dateComp.era, year: dateComp.year, month: dateComp.month, day: dateComp.day, hour: dateComp.hour, minute: dateComp.minute, second: 0, nanosecond: 0)

    var recurrenceComp:NSDateComponents?

    if let repeating = triggerInterval["repeating"] as? Bool {
        if repeating {
            recurrenceComp = NSDateComponents()

            if let intervalUnit = triggerInterval["unit"] as? String {
                if let trig = triggerInterval["integer"] as? String {
                    let trigInt = Int(trig)
                    switch intervalUnit {
                    case "minute":
                        recurrenceComp?.minute = trigInt!
                    case "hour":
                        recurrenceComp?.hour = trigInt!
                    case "day":
                        recurrenceComp?.day = trigInt!*7
                    case "week":
                        recurrenceComp?.day = trigInt!
                    case "month":
                        recurrenceComp?.month = trigInt!
                    case "year":
                        recurrenceComp?.year = trigInt!
                    default:
                        break
                    }
                }
            }
        }
    }

我的问题是，有没有人知道我只能指定一周的某些日子使用NSDateComponents并不一定是连续的？提前谢谢。