if you have ever tried synchronizing networked objects with SyncVars, there may have been instances where the object would synchronize fine for connected clients but not for late-joining client. Let's take a look at some code where this problem might occur. I have opened my WeaponSpawner class. Notice that I have a SyncVar of NetworkIdentity type named spawnedWeapon. In Update, I checked if spawnedWeapon is not null, then move it to the weapon holder position. The weapon holder is merely a child of this object. With this code, if spawnedWeapon exists, it should follow this object around. And here at the end, I just have a command to spawn the weapon and assign it to spawnedWeapon, which again is the SyncVar. How this code works isn't really important. I just want to show you that I am using a SyncVar for a NetworkIdentity, and that when that SyncVar contains a value, it will follow around this object. There's no reason this code shouldn't work, since SyncVars are synchronized to all clients, and even late-joining ones. However, this, in fact, will sometimes

break. So let's talk about that real quick. When an object is initialized over the network, that are about that object, including all of its synchronized properties. So, sink varis are included when the object is spawned. However, objects spawn in one at a time in any random order. Because of this, if you are synchronizing a network identity, that network identity object might not be spawned in before the script or object referencing it is in. Result: the synchronized network identity will be null because it simply does not exist yet. The scary part of this is that this is a race condition. Sometimes it will work, sometimes it will not. So you may never know that something is broken until it's far too late. I'm going to try and demonstrate this and hope that it breaks on my end so you can see the problem occur. I have a client host and a regular client open on builds on the server. I'm going to spawn a weapon. The weapon is spawned and as I move around my character, you can see that it is following on the client as well. It seems the code is working as expected.

let's connect a new client. The new client is connected, and you can see that it has the weapon too. The sync fair appears to be working, but watch what happens when I move around the character holding it. See how it's not updating on the new client. This is because the weapon didn't spawn in because it is a networked object, but the synchro property is null, so it doesn't know which weapon should be following the character. If you look at my console, you'll see a warning: Network identity net id 2 not found in spawn. This is the race condition I spoke of earlier. The character containing a reference to the sword spawned before the sword did, resulting in the network identity for the syncfare being unknown and could not be set. I have new builds up with the solution implemented. Let's see the difference. I'm going to spawn the sword, and I'm going to show you that it's working on late joining clients as well. When I connect a new client and then move around the sword owner, you can see that it's also

working on the late joining client for information on getting the full version of this tutorial, as well as dozens more, please check the description of this video.

Unity Multiplayer With Mirror - Fixing Networkidentity SyncVars/SyncList (Tutorial Preview)

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