try处理异常的三种方式

1.try方式
do {
  try //(可能异常代码)
} catch {
//系统提供的临时常量error
  print(error)
}

2.try?方式 如果异常返回nil,否则返回可选类
guard let anyObj = try? JSONSerialization.jsonObject(with: data, options: .mutableContainers) else { return }


 guard let exp = try? NSRegularExpression(pattern: "ac", options: .caseInsensitive) else { return }

3.try!方式 如果出现异常那么程序会崩溃
let anyObj = try! JSONSerialization.jsonObject(with: data, options: .mutableContainers) else { return }