Question

您好，有人可以解释一下一个对象如何通过NULL守卫，然后在尝试访问不可为空的字段时引发异常吗？（布尔）

您可以在上方方法中看到类型为response的对象Node不为空。请注意boolean字段IsArray !!

让我们看看当我们的response输入Deserialize方法时会发生什么：

                                   Passes null guard !!

然后在Null Reference Exception上以non-nullable field崩溃。正是在我说过要重点关注的字段上：boolean IsArray。

堆栈跟踪

{System.NullReferenceException: Object reference not set to an instance of an object.
   at redius.Node.get_Kind() in D:\Work\redius\core\redius\Internals\Resp\Node.cs:line 15
   at redius.Node.get_IsArray() in D:\Work\redius\core\redius\Internals\Resp\Node.cs:line 22
   at redius.Deserializer.List.Deserialize(Node node) in D:\Work\redius\core\redius\Internals\Formatter\Deserializer\Deserializer.List.cs:line 19}

有人可以解释一下这怎么可能吗？下面是Node类型：

public abstract partial class Node : IEquatable<Node> {

        public enum Discriminator {
            String,
            Integer,
            Array
        }

        public Discriminator Kind => this.NodeKind;
        protected abstract Discriminator NodeKind { get; }

        public Node.Array AsArray => this as Node.Array;
        public Node.Integer AsInteger => this as Node.Integer;
        public Node.String AsString => this as String;

        public bool IsArray => this.Kind == Discriminator.Array;
        public bool IsString => this.Kind == Discriminator.Integer;
        public bool IsInteger => this.Kind == Discriminator.String;

        #region IRAW

        protected virtual ReadOnlyMemory<byte> GetRaw() {
            return new byte[] { };
        }

        #endregion

        public bool Equals(Node other) {
            if (this.Kind != other.Kind) {
                return false;
            }
            bool result;
            switch (other.Kind) {
                case Discriminator.Array: result = this.AsArray.Equals(other.AsArray); break;
                case Discriminator.Integer: result = this.AsInteger.Equals(other.AsInteger); break;
                case Discriminator.String: result = this.AsString.Equals(other.AsString); break;

                default: throw new NotImplementedException();
            }
            return result;
        }

    }

PS：：当Node进入Deserialize方法时，调试器出现问题，因为我无法访问它（无法访问其字段）！

PS 2 如果我尝试在Deserializer方法中添加以下行：
var values = node.GetType().GetFields().Select(x => x.GetValue(node));
应用程序进入中断状态，并且出现以下异常：
System Execution Engine Exception

通过空防护的对象上的系统执行引擎异常

0 个答案: