Blackboard Variable changed condition

[sinzer0Participant]

I’m trying to create a condition task that returns true when a BB variable changes. Everything works except OnDisabled gets called after the transition in a FSM. So in this case where should I unsubscribe from the OnValueChanged event to clean up the event listener?

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namespace Game.Tasks.Conditions {     [Name("On Variable Changed")]     [Category("✫ Blackboard")]     public class BBVariableChanged : ConditionTask     {                [BlackboardOnly]         public BBParameter<object> BBVar;           protected override string info         {             get { return BBVar + " Changed."; }         }           protected override string OnInit()         {             if(BBVar != null)             {                 BBVar.varRef.onValueChanged += OnValueChanged;                 YieldReturn(true);             }             else{                 Debug.LogWarning("Blackboard Variable not set.");             }             return base.OnInit();         }           protected override bool OnCheck()         {             return false;         }           protected override void OnDisable()         {               if (BBVar != null)             {                 BBVar.varRef.onValueChanged -= OnValueChanged;             }             base.OnDisable();         }           private void OnValueChanged(string arg1, object arg2)         {             YieldReturn(true);         }     } }

[GavalakisKeymaster]

Hello and sorry for the late reply.

I have modified your code to work as I expect you want it to:

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using NodeCanvas.Framework; using ParadoxNotion.Design; using UnityEngine;   namespace Game.Tasks.Conditions {     [Name("On Variable Changed")]     [Category("✫ Blackboard")]     public class BBVariableChanged : ConditionTask     {                [BlackboardOnly]         public BBParameter<object> BBVar;           protected override string info{             get { return BBVar + " Changed."; }         }           protected override string OnInit(){             if (BBVar.isNone){ return "Blackboard Variable not set."; } return null;         }   protected override void OnEnable(){ BBVar.varRef.onValueChanged += OnValueChanged; }           protected override void OnDisable(){ BBVar.varRef.onValueChanged -= OnValueChanged;         }           protected override bool OnCheck(){             return false;         }           private void OnValueChanged(string arg1, object arg2){             YieldReturn(true);         }     } }

Some notes:
– Use OnInit only for initialization similar to Unity’s Awake.
– Use OnEnable and OnDisable to subscribe and unsubscribe.
– You don’t have to call base implementation of methods.
– A BBParameter will never be null. Use .isNone to determine if the front-end user has selected a variable or not.

Let me know if that works for you.
Thanks!

[sinzer0Participant]

Thanks that works now for normal conditions but I did notice one issue. When the condition is part of a Concurrent node OnEnable is not called but OnInit is. Thus the condition does not work in Concurrent nodes because the event never gets setup.

Not sure if that is a bug or working as intended?

[GavalakisKeymaster]

Hello and sorry for the late reply.
You are correct. This is actually a bug in the Concurrent Node.

To fix this, please open up ConcurrentState.cs file and:
1) In the OnEnter Method, add this line of code above everything else:
conditionList.Enable(graphAgent, graphBlackboard);

2) In the OnExit method, add this line of code first as well:
conditionList.Disable();

Thanks for the report!

[Author]

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