Swift 2.0中的'advancedBy'API

Question

Swift 2.0中已删除'advance'API.

如果我们在Swift 2.0中使用'advance'API,就会抛出错误说法'advance' is unavailable: call the '**advancedBy(n)**' method on the index.

如何在Swift 2.0中使用advancedBy API获取索引？

以下是我的情景:

let startIndex = advance(cardNumber.endIndex, -4) 
let lastFourDigitsOfPhoneNumber = phoneNumber.substringFromIndex(startIndex)

Answer 1

你需要调用advancedBy上endIndex.

let startIndex = cardNumber.endIndex.advancedBy(-4)
let lastFourDigitsOfPhoneNumber = phoneNumber.substringFromIndex(startIndex)