如何在循环中执行多个保护语句？

Question

如何在不中断循环的情况下在循环中执行多个guard语句？如果一个保护语句失败,它会将我踢出当前循环迭代并绕过剩余的代码.

for user in users {
    guard let first = user["firstName"] as? String else {
        print("first name has not been set")
        continue
    }
    print(first)

    guard let last = user["lastName"] as? String else {
        print("last name has not been set")
        continue
    }
    print(last)

    guard let numbers = user["phoneNumbers"] as? NSArray else {
        print("no phone numbers were found")
        continue
    }
    print(numbers)
}

如何确保为每个用户执行所有语句？在else块中放置return和break也不起作用.谢谢!

Answer 1

guard语句的目的是检查条件(或尝试解包一个可选项),如果该条件为false或选项为nil,则您要退出当前作用域.

想象一下,警卫声明(用甘道夫的声音说)"如果你不符合这个条件你就不会过去......"

你想在这里做什么可以简单地用if let语句完成:

for user in users {
  if let first = user["firstName"] as? String {
    print(first)
  } else {
    print("first name has not been set")
  }
  //Do the same for the other fields
}

需要注意的一点是,guard letguard语句中允许您在guard语句之后访问未包装的值,因为if let只允许您在下一个块中访问该值.