Keeping blackboards on prefab instances in sync with the base prefab

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  • October 9, 2020 at 11:43 am #16105
    yookaharold
    Participant

      Hi, I can’t find any posts about this problem, so…

      Here’s the setup…

      • We make gameplay prefabs that use Node/FlowCanvas
      • These prefabs are re-used multiple times on multiple levels
      • A simple example from Mario would be the ? block – an object with some functionality that is used all over the game
      • These have blackboards (obviously) with several variables
      • Many of these variables are designed to be overridden, so that the prefab instances in the level can do something different to the defaults set on the base prefab
      • Using the Mario example again, the first ? block in the level might spawn a coin, the next one in the level might spawn a mushroom – so the ObjectToSpawn variable would be overridden
      • As a result, we have a large number of prefab instances that have blackboards with overridden variables

      So far, so good. However…

      • If we change the order of the variables on the base prefab, the blackboard on any prefab instance that also has overridden variables get messed up – variables are changed or disappear entirely
      • The result is that we must manually fix up each broken prefab instance, which is very time consuming as they are used all over the place and makes it a real risk to make any changes to the base prefab after it has been used on levels

      We really need blackboards to be 100% rock solid – able to deal with adding, removing, moving and renaming variables without causing all prefab instances to break.

      Is this a bug, or expected behaviour, or is there something that I have missed?

      October 12, 2020 at 11:36 am #16110
      driiade
      Participant

        I up vote this.

        We totally disabled the possibility to have Variant on prefab with blackboard, it was much more difficult to fix blackboard than applying change on variant.

        As a result, level designer use special scripts to override blackboard value in their level, which is a weird hot fix.

        October 12, 2020 at 12:55 pm #16109
        yookaharold
        Participant

          [quote quote=15337]…level designer use special scripts to override blackboard value in their level, which is a weird hot fix. [/quote]

          That’s interesting. We were thinking of doing something similar and that’s why I asked the question here, as we don’t really want to have to do that!

          October 16, 2020 at 5:19 pm #16108
          Gavalakis
          Keymaster

            Hello guys,

            Indeed, re-ordering the variables of prefab assets when some of the variables in the prefab instance are overridden, can mess up the variables in the prefab instance. This is specifically true when the re-ordered variable “pass over” an overridden variable. In the new version (just released), I have unfortunately disabled re-ordering in prefabs to avoid accidents, but meanwhile I do also look into refactoring the whole serialization of blackboard variables once again, in hopes to handle this better. I do have an idea that I think will work but it needs some time to work on it. As such, the disabled re-ordering for prefabs is a temporary measure until I’ve tested and implement that new way of handling variables.

            Thanks!

            January 23, 2025 at 2:23 am #16107
            teddydief
            Participant

              Hi! I’m new to NodeCanvas, and really enjoying it.

              I’m using an increasingly large number of Blackboard Variables on a Prefab (not Graph Variables), and am wondering if you ended up adding a way to enable reordering of them? Perhaps only when editing in the prefab itself (not an instance)? I can see how this is tricky to implement. Just curious if you added functionality that I’m missing.

              I’m using NodeCanvas v3.31

              February 3, 2025 at 4:51 pm #16106
              Gavalakis
              Keymaster

                Hello and welcome! I’m glad you enjoy NodeCanvas! 🙂
                Even though there was a lot of refactoring and updates since back then, the last time I tried implementing this, it was unfortunately still a pain as to keep it safe in the frontend :-/ I will give this another look however!
                Thanks!

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