swift 2.0 advance用法

Question

let str = "Hello world!"
let index = advance(str.startindex, 7)//这个报错
求具体怎么改

Answer 1

把advance方法改成advancedBy

let str = "Hello world!"
//let index = advance(str.startindex, 7)
let index = str.startIndex.advancedBy(7)