Question

我正在尝试序列化具有不可变基类的不可变消息。但是，我无法说服protobuf-serializer将其反序列化为派生类型。简而言之，这个测试给了我一个无效的强制转换异常（从Base到Derived）：

[TestFixture]
public class InheritanceTest
{
    public class Base
    {
        public int IntField { get; private set; }

        public Base(int intField)
        {
            IntField = intField;
        }
    }

    public class Derived : Base
    {
        public string StringField { get; private set; }

        public Derived(int intField, string stringField) : base(intField)
        {
            StringField = stringField;
        }
    }

    [Test]
    public void TestInheritance()
    {
        var serializer = TypeModel.Create();
        serializer.Add(typeof (Base), true)
            .Add(1, "IntField")
            .AddSubType(2, typeof (Derived))
            .UseConstructor = false;

        serializer.Add(typeof (Derived), true)
            .Add(1, "StringField")
            .UseConstructor = false;

        serializer.CompileInPlace();

        using (var stream = new MemoryStream())
        {
            var message = new Derived(1, "Some text that is not important");

            serializer.Serialize(stream, message);
            stream.Position = 0;

            var retrieved = (Derived) serializer.Deserialize(stream, null, typeof (Derived));

            Assert.AreEqual(message.IntField, retrieved.IntField);
            Assert.AreEqual(message.StringField, retrieved.StringField);
        }
    }

}

如果我将Base和Derived转换为可变类型，则此异常消失。我做错了什么或者它是protobuf-net的限制吗？

Answer 1

  [TestFixture]
public class InheritanceTest
{
    public class Base
    {
        public int IntField { get; private set; }

        public Base(int intField)
        {
            IntField = intField;
        }
    }

    public class Derived : Base
    {
        public string StringField { get; private set; }

        public Derived(int intField, string stringField) : base(intField)
        {
            StringField = stringField;
        }
    }

    [Test]
    public void TestInheritance()
    {
        var serializer = TypeModel.Create();
        serializer.Add(typeof (Base), true)
            .Add(1, "IntField")
            .UseConstructor = false;

        serializer.Add(typeof (Derived), true)
            .Add(1, "StringField")
            .UseConstructor = false;

        serializer.CompileInPlace();

        using (var stream = new MemoryStream())
        {
            var message = new Derived(1, "Some text that is not important");

            serializer.Serialize(stream, message);
            stream.Position = 0;

            var retrieved = (Derived) serializer.Deserialize(stream, null, typeof (Derived));

            Assert.AreEqual(message.IntField, retrieved.IntField);
            Assert.AreEqual(message.StringField, retrieved.StringField);
        }
    }

}

或

  [TestFixture]
    public class InheritanceTest
    {
        [DataContract]
        public class Base
        {
            [DataMember(Order = 1)]
            public int IntField { get; private set; }

            public Base(int intField)
            {
                IntField = intField;
            }
            protected Base(){}
        }

        [DataContract]
        public class Derived : Base
        {
            [DataMember(Order = 3)]
            public string StringField { get; private set; }

            public Derived(int intField, string stringField) : base(intField)
            {
                StringField = stringField;
            }
            private Derived(){}
        }

        [Test]
        public void TestInheritance()
        {
            RuntimeTypeModel.Default.Add(typeof(Base), true).AddSubType(2, typeof(Derived));

             using (var stream = new MemoryStream())
                {
                    var message = new Derived(1, "Some text that is not important");

                    Serializer.Serialize(stream, message);
                    stream.Position = 0;

                    var retrieved = Serializer.Deserialize<Derived>(stream);            

                    Assert.AreEqual(message.IntField, retrieved.IntField);
                    Assert.AreEqual(message.StringField, retrieved.StringField);
            }
        }

    }

Answer 2

这看起来是元组检测的副作用，导致它具有特定的代码分支。好的是，您应该可以通过将true更改为false来解决原始代码中的问题。此参数告诉您是否应用标准行为。您不需要，因为您自己定义模型。

        var serializer = TypeModel.Create();
        serializer.Add(typeof (Base), false)
            .Add(1, "IntField")
            .AddSubType(2, typeof (Derived))
            .UseConstructor = false;

        serializer.Add(typeof (Derived), false)
            .Add(1, "StringField")
            .UseConstructor = false;

注意我还没有证实这一点 - 我稍后会检查。

Protobuf-net和不可变消息的继承

2 个答案: