swift Range init函数错误

我的代码

self.p_formatterTime = self.pubTime?.substringWithRange(Range<Int>(start: 5, end: 11))

self.p_formatterTime=self.pubTime？.substringWithRange（范围（开始：5，结束：11））

编译错误消息：

Cannot invoke initializer for type 'Range<Int>' with an argument list of type '(start: Int, end: Int)'

无法使用类型为“（start:Int，end:Int）”的参数列表调用类型“Range”的初始值设定项

如何修复

if let a = self.pubTime {
    self.p_formatterTime = a.substringWithRange(Range<String.Index>(start: a.startIndex.advancedBy(5), end: a.startIndex.advancedBy(11)))
    // ...
}

let myString = "0123456789ABCDEFG"
let mySubString = myString.substringWithRange(Range<String.Index>(start: myString.startIndex.advancedBy(5), end: myString.startIndex.advancedBy(11)))
print(mySubString) // prints "56789A"