get 请求编码 格式
et url = "https://www.google.com/search?q=成都市"//编码
//let url = appStoreURL.addingPercentEscapes(using: String.Encoding.utf8) //iOS7之前
let newUrl = url.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed)! // iOS 9之后。
print("编码过后的url:\(newUrl)") //编码过后的url:https://www.google.com/search? q=%E6%88%90%E9%83%BD%E5%B8%82
