Question

早上好

自从时间开始以来，人们一直希望并发明了在Flash AS3中进行枚举的方法。

许多尝试都存在各种问题，例如能否使用构造函数创建新类型的枚举（不安全）。

我相信以下在编译时是类型安全的，并且无法在运行时创建枚举类的新实例。

主要问题是AS3无法拥有私有构造函数。在这个例子中，构造函数只有在传递私有静态const变量ENFORCER时才能成功，该变量只在类内部可见。

package
{
    public class PermissionsEnum
    {

        private static const ENFORCER = new Object();

        public static const READ:PermissionsEnum = new PermissionsEnum(ENFORCER, 1);
        public static const WRITE:PermissionsEnum = new PermissionsEnum(ENFORCER, 2);
        public static const CREATE:PermissionsEnum = new PermissionsEnum(ENFORCER, 4);
        public static const DELETE:PermissionsEnum = new PermissionsEnum(ENFORCER, 8);

        private var _value:uint;

        public function PermissionsEnum(e:Object, v:uint)
        {
            if (e != ENFORCER)
                throw new Error("Attempted enum security breach.");

            this._value = v;
        }

        public function get value() : uint
        {
            return this._value;
        }

    }

}

评论任何人？

其他先前的尝试允许某种循环引用（顺便提一下，Java编译器不允许，并且C＃编译器允许）作为尝试禁止运行时创建更多枚举值。我认为这更美丽。

我们怎么想？

富

Answer 1

您可以在构造函数中使用更严格的编译时限制（以下所有代码都在同一个PermissionsEnum.as文件中）：

package
{
public class PermissionsEnum
{

    private static const ENFORCER:Enforcer = new Enforcer();

    public static const READ:PermissionsEnum = new PermissionsEnum(ENFORCER, 1);
    public static const WRITE:PermissionsEnum = new PermissionsEnum(ENFORCER, 2);
    public static const CREATE:PermissionsEnum = new PermissionsEnum(ENFORCER, 4);
    public static const DELETE:PermissionsEnum = new PermissionsEnum(ENFORCER, 8);

    private var _value:uint;

    public function PermissionsEnum(e:Enforcer, v:uint)
    {
        this._value = v;
    }

    public function get value() : uint
    {
        return this._value;
    }

}
}

class Enforcer
{
}

Answer 2

1）如何将值转换为枚举成员？

2）我在创建PermissionsEnum时遇到一个问题：对其内部值没有共同控制。我的意思是，如果我在枚举中有5-10个成员，那么找到重复的值就没有问题了。但如果列表增长，那么在源代码中出错的机会也会消失：

public static const READ:PermissionsEnum = new PermissionsEnum(ENFORCER, 1);
public static const WRITE:PermissionsEnum = new PermissionsEnum(ENFORCER, 7);
public static const APPEND:PermissionsEnum = new PermissionsEnum(ENFORCER, 15);
public static const CREATE:PermissionsEnum = new PermissionsEnum(ENFORCER, 8);
public static const DELETE:PermissionsEnum = new PermissionsEnum(ENFORCER, 3);
public static const COMMIT:PermissionsEnum = new PermissionsEnum(ENFORCER, 6);
public static const SUBMIT:PermissionsEnum = new PermissionsEnum(ENFORCER, 21);
public static const POP:PermissionsEnum = new PermissionsEnum(ENFORCER, 22);
public static const PUSH:PermissionsEnum = new PermissionsEnum(ENFORCER, 3);
public static const SELECT:PermissionsEnum = new PermissionsEnum(ENFORCER, 17);
public static const DESELECT:PermissionsEnum = new PermissionsEnum(ENFORCER, 22);
public static const END:PermissionsEnum = new PermissionsEnum(ENFORCER, 15);

RFC - Flash AS3中的安全枚举

2 个答案: