表达太复杂，无法在合理的时间内解决;

Question

我刚从Xcode 8.3升级到Xcode 9.4并且它一直保持索引直到它崩溃，然后输出错误。

  斯威夫特 - 表达太复杂，无法在合理的时间内解决;   考虑将表达式分解为不同的子表达式

这是Xcode 9和Swift 4.1中的错误吗？

 let fromString = convenience.getTimeAsString(timeStamp: timeStampDateAndTime, timeFormat: "HH:mm")
    let toString = convenience.getTimeAsString(timeStamp: toTimeStamp, timeFormat: "HH:mm")

   var cellData = "Booking: " + booking.BookingNumber + "\n" + "Area: " + booking.Locality + "\n" + "Postcode: " + booking.PostCode + "\n" + "Time: " + fromString + " - " + toString

我如何修理？

  var cellData = " \("Booking: ") \(booking.BookingNumber) \("\n") \("Area: ") \(booking.Locality) \("\n") \("Postcode: ") \(booking.PostCode) \("\n") \("Time: ") \(fromString) \(" - ") \(toString) "