Code Generation

So for this script:

using Mirage;

public class Data : NetworkBehaviour
{
    [SyncVar(hook = nameof(OnInt1Changed))]
    public int int1 = 66;

    [SyncVar]
    public int int2 = 23487;

    [SyncVar]
    public string MyString = "Example string";

    void OnInt1Changed(int oldValue, int newValue)
    {
        // do something here
    }
}

The following sample shows the code that is generated by Mirage for the SerializeSyncVars function which is called inside NetworkBehaviour.OnSerialize:

public override bool SerializeSyncVars(NetworkWriter writer, bool initialState)
{
    // Write any SyncVars in base class
    bool written = base.SerializeSyncVars(writer, forceAll);

    if (initialState)
    {
        // The first time a game object is sent to a client, send all the data (and no dirty bits)
        writer.WritePackedUInt32((uint)this.int1);
        writer.WritePackedUInt32((uint)this.int2);
        writer.Write(this.MyString);
        return true;
    }
    else 
    {
        // Writes which SyncVars have changed
        writer.WritePackedUInt64(base.syncVarDirtyBits);

        if ((base.get_syncVarDirtyBits() & 1u) != 0u)
        {
            writer.WritePackedUInt32((uint)this.int1);
            written = true;
        }

        if ((base.get_syncVarDirtyBits() & 2u) != 0u)
        {
            writer.WritePackedUInt32((uint)this.int2);
            written = true;  
        }

        if ((base.get_syncVarDirtyBits() & 4u) != 0u)
        {
            writer.Write(this.MyString);
            written = true;     
        }

        return written;
    }
}

The following sample shows the code that is generated by Mirage for the DeserializeSyncVars function which is called inside NetworkBehaviour.OnDeserialize:

public override void DeserializeSyncVars(NetworkReader reader, bool initialState)
{
    // Read any SyncVars in base class
    base.DeserializeSyncVars(reader, initialState);

    if (initialState)
    {
        // The first time a game object is sent to a client, read all the data (and no dirty bits)
        int oldInt1 = this.int1;
        this.int1 = (int)reader.ReadPackedUInt32();
        // if old and new values are not equal, call hook
        if (!base.SyncVarEqual<int>(num, ref this.int1))
        {
            this.OnInt1Changed(num, this.int1);
        }

        this.int2 = (int)reader.ReadPackedUInt32();
        this.MyString = reader.ReadString();
        return;
    }

    int dirtySyncVars = (int)reader.ReadPackedUInt32();
    // is 1st SyncVar dirty
    if ((dirtySyncVars & 1) != 0)
    {
        int oldInt1 = this.int1;
        this.int1 = (int)reader.ReadPackedUInt32();
        // if old and new values are not equal, call hook
        if (!base.SyncVarEqual<int>(num, ref this.int1))
        {
            this.OnInt1Changed(num, this.int1);
        }
    }

    // is 2nd SyncVar dirty
    if ((dirtySyncVars & 2) != 0)
    {
        this.int2 = (int)reader.ReadPackedUInt32();
    }

    // is 3rd SyncVar dirty
    if ((dirtySyncVars & 4) != 0)
    {
        this.MyString = reader.ReadString();
    }
}

If a NetworkBehaviour has a base class that also has serialization functions, the base class functions should also be called.