Netcode升级到1.2.0网络变量的变化的变化

1 概述

最近工程升级到Netcode For Gameobject 1.2.0版本
运行会出现部分报错，查看原因后发现是网络变量模块构造方法出现的问题

2 继承网络变量 NetworkVariable，派生类构造出错的问题

2.1 代码描述

【1.1.0+版本 标记以下类为过时】
【1.0.2-版本 以下类可用】
/// 

/// 网络变量 - 基类【重写】
/// 
/// 
/// 
/// 
///  加入构造函数，可以new新元素加入链表
/// 网络变量可以用作静态字段，但是RPC不可以
/// 
 /// 
[Serializable]
public class NetVar<T> : NetworkVariable<T> where T : unmanaged
{
    public NetVar(T value = default,
         NetworkVariableReadPermission readPerm = DefaultReadPerm,
         NetworkVariableWritePermission writePerm = DefaultWritePerm) : 
base(value, readPerm, writePerm)
    {
        Value = value;
    }
}

[Obsolete("1.0.2-版本可用，1.1+版本使用-NetworkVariable")]
[Serializable] public class NetVar_Int : NetVar<int>
{
     public NetVar_Int(int value = 0,
     NetworkVariableReadPermission readPerm = DefaultReadPerm,
     NetworkVariableWritePermission writePerm = DefaultWritePerm) : base(value, readPerm, writePerm)
     {
         Value = value;
     }
}

2.2 问题记录

1 自己定义的类继承网络变量【NetworkVariable】
1.1使用自定义的类，构造时会直接报错，新版本的网络变量内部有改动

NetVar<int> nv_hp = new NetVar<int>();  **[1.0版本以前可用]**

2.3 解决办法：使用 NetworkVariable 即可

NetworkVariable<int> nv_hp = new NetworkVariable<int>(); [1.1、1.2版本可用]

3 网络变量 NetworkVariable 类的版本差异比较

3.1 差异说明

显著的变化在T Value赋值的过程，和对T的限定，变得更加安全
比较值得方法不一样，但是均在值比较之后发生变化才赋值，无变化不触发。

3.2 [1.0.2]版本的网络变量

using System;
using System.Runtime.CompilerServices;
using Unity.Collections.LowLevel.Unsafe;
using UnityEngine;

namespace Unity.Netcode
{
	[Serializable]
	public class NetworkVariable<T> : NetworkVariableBase where T : unmanaged
	{
		public delegate void OnValueChangedDelegate(T previousValue, T newValue);

		public OnValueChangedDelegate OnValueChanged;

		[SerializeField]
		private protected T m_InternalValue;

		public virtual T Value
		{
			get
			{
				return m_InternalValue;
			}
			set
			{
				if (!ValueEquals(ref m_InternalValue, ref value))
				{
					if ((bool)m_NetworkBehaviour && !CanClientWrite(m_NetworkBehaviour.NetworkManager.LocalClientId))
					{
						throw new InvalidOperationException("Client is not allowed to write to this NetworkVariable");
					}

					Set(value);
				}
			}
		}

		public NetworkVariable(T value = default(T), NetworkVariableReadPermission readPerm = NetworkVariableReadPermission.Everyone, NetworkVariableWritePermission writePerm = NetworkVariableWritePermission.Server)
			: base(readPerm, writePerm)
		{
			m_InternalValue = value;
		}

		[MethodImpl(MethodImplOptions.AggressiveInlining)]
		private unsafe static bool ValueEquals(ref T a, ref T b)
		{
			void* ptr = UnsafeUtility.AddressOf(ref a);
			void* ptr2 = UnsafeUtility.AddressOf(ref b);
			return UnsafeUtility.MemCmp(ptr, ptr2, sizeof(T)) == 0;
		}

		private protected void Set(T value)
		{
			SetDirty(isDirty: true);
			T internalValue = m_InternalValue;
			m_InternalValue = value;
			OnValueChanged?.Invoke(internalValue, m_InternalValue);
		}

		public override void WriteDelta(FastBufferWriter writer)
		{
			WriteField(writer);
		}

		public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
		{
			T internalValue = m_InternalValue;
			NetworkVariableSerialization<T>.Read(reader, out m_InternalValue);
			if (keepDirtyDelta)
			{
				SetDirty(isDirty: true);
			}

			OnValueChanged?.Invoke(internalValue, m_InternalValue);
		}

		public override void ReadField(FastBufferReader reader)
		{
			NetworkVariableSerialization<T>.Read(reader, out m_InternalValue);
		}

		public override void WriteField(FastBufferWriter writer)
		{
			NetworkVariableSerialization<T>.Write(writer, ref m_InternalValue);
		}
	}
}

3.3 [1.2.0]版本的网络变量

using System;
using UnityEngine;

namespace Unity.Netcode
{
	[Serializable]
	public class NetworkVariable<T> : NetworkVariableBase
	{
		public delegate void OnValueChangedDelegate(T previousValue, T newValue);

		public OnValueChangedDelegate OnValueChanged;

		[SerializeField]
		private protected T m_InternalValue;

		public virtual T Value
		{
			get
			{
				return m_InternalValue;
			}
			set
			{
				if (!NetworkVariableSerialization<T>.AreEqual(ref m_InternalValue, ref value))
				{
					if ((bool)m_NetworkBehaviour && !CanClientWrite(m_NetworkBehaviour.NetworkManager.LocalClientId))
					{
						throw new InvalidOperationException("Client is not allowed to write to this NetworkVariable");
					}

					Set(value);
				}
			}
		}

		public NetworkVariable(T value = default(T), NetworkVariableReadPermission readPerm = NetworkVariableReadPermission.Everyone, NetworkVariableWritePermission writePerm = NetworkVariableWritePermission.Server)
			: base(readPerm, writePerm)
		{
			m_InternalValue = value;
		}

		private protected void Set(T value)
		{
			SetDirty(isDirty: true);
			T internalValue = m_InternalValue;
			m_InternalValue = value;
			OnValueChanged?.Invoke(internalValue, m_InternalValue);
		}

		public override void WriteDelta(FastBufferWriter writer)
		{
			WriteField(writer);
		}

		public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
		{
			T internalValue = m_InternalValue;
			NetworkVariableSerialization<T>.Read(reader, ref m_InternalValue);
			if (keepDirtyDelta)
			{
				SetDirty(isDirty: true);
			}

			OnValueChanged?.Invoke(internalValue, m_InternalValue);
		}

		public override void ReadField(FastBufferReader reader)
		{
			NetworkVariableSerialization<T>.Read(reader, ref m_InternalValue);
		}

		public override void WriteField(FastBufferWriter writer)
		{
			NetworkVariableSerialization<T>.Write(writer, ref m_InternalValue);
		}
	}
}