qq_31138973的博客

import UIKitvar str = "Hello, playground"let index1 = str.index(str.startIndex, offsetBy: 7)let subStr1 = str.substring(from: index1) //subStr1结果为 playground let index2 = str.index(str.endIndex, offset

1.判断字典中是否含有某个key值 import UIKitlet dict: NSDictionary = ["key1":"zhang","key2":"zhong"]//第一种方法：swift3.0的方法 let X: Bool = dict.allKeys.contains { (key) -> Bool in print(key) if key as! String ==