tracker_device: Quest Objectives That Actually Track Progress

Overview

The tracker_device solves a common island-design problem: how do I show players what they need to do and how far along they are? Placing a tracker in your level gives you:

• A HUD widget (title + description + progress bar) that appears automatically when the device is assigned to a player.
• A target value (0–10 000) that, when reached, fires CompleteEvent and can trigger downstream devices.
• Verse API methods to assign/remove the tracker, increment or set the value, query state, and even persist progress between sessions.

When to reach for it:

• Eliminate N guards → tracker counts eliminations.
• Collect N items → tracker counts pickups.
• Shared team objective → set Sharing to Team or All in device settings.
• Persistent daily quest → enable Use Persistence and call Save/Load.

API Reference

tracker_device

Allows creation and HUD tracking of custom objectives for agents to complete.

Full public surface, resolved verbatim from the live Epic digest (Fortnite.digest.verse).

tracker_device<public> := class<concrete><final>(creative_device_base):

Events (subscribe a handler to react):

Methods (call these to make the device act):

Walkthrough

Scenario: Stronghold Defense — Eliminate 5 Guards to Win

A player enters the island, the tracker is assigned to them, and every time they eliminate a guard (signaled by a trigger_device wired to each guard spawner's elimination output) the tracker increments. When the count hits 5 the tracker completes, the vault door unlocks, and a congratulations message appears on the HUD.

using { /Fortnite.com/Devices }
using { /Verse.org/Simulation }
using { /Verse.org/Native }

# Helper so we can pass localized text to SetTitleText / SetDescriptionText
ElimTitle<localizes>(S : string) : message = "{S}"
ElimDesc<localizes>(S : string) : message = "{S}"

stronghold_tracker_manager := class(creative_device):

    # ── Editable device references ────────────────────────────────────────
    @editable
    GuardEliminatedTrigger : trigger_device = trigger_device{}
    # This trigger fires once per guard eliminated (wire it in the editor)

    @editable
    VaultDoorLock : lock_device = lock_device{}
    # The vault door that unlocks when the objective completes

    @editable
    ObjectiveTracker : tracker_device = tracker_device{}
    # The tracker_device placed in the level

    # ── Lifecycle ─────────────────────────────────────────────────────────
    OnBegin<override>()<suspends> : void =
        # 1. Set the HUD title and description (both take `message` values)
        ObjectiveTracker.SetTitleText(ElimTitle("Stronghold Defense"))
        ObjectiveTracker.SetDescriptionText(ElimDesc("Eliminate the guards!"))

        # 2. Set the target: 5 guards must be eliminated
        ObjectiveTracker.SetTarget(5)

        # 3. Assign the tracker to every player currently in the game
        ObjectiveTracker.AssignToAll()

        # 4. React when a guard is eliminated
        GuardEliminatedTrigger.TriggeredEvent.Subscribe(OnGuardEliminated)

        # 5. React when the tracker reaches its target
        ObjectiveTracker.CompleteEvent.Subscribe(OnObjectiveComplete)

    # ── Event handlers ────────────────────────────────────────────────────

    # Called each time the guard-eliminated trigger fires.
    # TriggeredEvent sends ?agent, so we unwrap it before using it.
    OnGuardEliminated(TriggeringAgent : ?agent) : void =
        if (A := TriggeringAgent?):
            # Increment uses the device's "Amount to Change on Received Signal"
            # setting (default 1), so each call adds 1 to that agent's count.
            ObjectiveTracker.Increment(A)

    # Called when an agent's tracked value reaches the target (5).
    # CompleteEvent sends a plain `agent` (not optional).
    OnObjectiveComplete(CompletingAgent : agent) : void =
        # Unlock the vault door for everyone
        VaultDoorLock.Unlock(CompletingAgent)

        # Update the HUD description to celebrate
        ObjectiveTracker.SetDescriptionText(ElimDesc("Stronghold cleared!"))

        # Remove the tracker from all players so the bar disappears
        ObjectiveTracker.RemoveFromAll()

Line-by-line explanation:

Common patterns

Pattern 1 — Query progress and conditionally boost the target

After a reinforcement wave spawns, raise the target by 3 so players have more guards to eliminate. Use GetValue and GetTarget to log current state, and IncreaseTargetValue to bump the target per-agent.

using { /Fortnite.com/Devices }
using { /Verse.org/Simulation }
using { /Verse.org/Native }

reinforcement_wave_handler := class(creative_device):

    @editable
    ReinforcementTrigger : trigger_device = trigger_device{}
    # Fires when the reinforcement wave spawns

    @editable
    ObjectiveTracker : tracker_device = tracker_device{}

    OnBegin<override>()<suspends> : void =
        ReinforcementTrigger.TriggeredEvent.Subscribe(OnReinforcementsArrived)

    OnReinforcementsArrived(TriggeringAgent : ?agent) : void =
        # Get every agent currently assigned to this tracker
        ActiveAgents := ObjectiveTracker.GetActiveAgents()

        for (A : ActiveAgents):
            # Only raise the bar for agents who haven't finished yet
            if (not ObjectiveTracker.HasReachedTarget[A]):
                # Current target before we change it
                CurrentTarget := ObjectiveTracker.GetTarget()
                # Current value for this specific agent
                CurrentValue  := ObjectiveTracker.GetValue(A)

                # Raise the target by 3 (call IncreaseTargetValue three times)
                ObjectiveTracker.IncreaseTargetValue(A)
                ObjectiveTracker.IncreaseTargetValue(A)
                ObjectiveTracker.IncreaseTargetValue(A)

Key calls: GetActiveAgents(), HasReachedTarget[] (failable — used in if (not …)), GetTarget(), GetValue(Agent), IncreaseTargetValue(Agent).

Pattern 2 — Persistent daily quest: save and load progress

Enable Use Persistence on the tracker in the editor, then call Load when a player joins and Save whenever they make progress. Progress survives across sessions.

using { /Fortnite.com/Devices }
using { /Verse.org/Simulation }
using { /Verse.org/Native }

DailyQuestTitle<localizes>(S : string) : message = "{S}"
DailyQuestDesc<localizes>(S : string)  : message = "{S}"

daily_quest_manager := class(creative_device):

    @editable
    QuestTracker : tracker_device = tracker_device{}
    # Must have "Use Persistence" = Use in device settings

    @editable
    CollectTrigger : trigger_device = trigger_device{}
    # Fires when the player collects a quest item

    OnBegin<override>()<suspends> : void =
        QuestTracker.SetTitleText(DailyQuestTitle("Daily Quest"))
        QuestTracker.SetDescriptionText(DailyQuestDesc("Collect 10 crystals"))
        QuestTracker.SetTarget(10)

        # Load saved progress for ALL players who are already in the session
        QuestTracker.LoadForAll()

        CollectTrigger.TriggeredEvent.Subscribe(OnItemCollected)
        QuestTracker.CompleteEvent.Subscribe(OnQuestComplete)

    OnItemCollected(TriggeringAgent : ?agent) : void =
        if (A := TriggeringAgent?):
            if (QuestTracker.IsActive[A]):
                QuestTracker.Increment(A)
                # Persist the new value immediately
                QuestTracker.Save(A)

    OnQuestComplete(A : agent) : void =
        # Clear persistence so the quest resets tomorrow
        QuestTracker.ClearPersistence(A)
        QuestTracker.Remove(A)

Key calls: LoadForAll(), IsActive[] (failable — used inside if), Increment(Agent), Save(Agent), ClearPersistence(Agent), Remove(Agent).

Pattern 3 — Force-set a value and immediately complete for a specific agent

Sometimes a power-up should instantly finish the objective for one player (e.g., they found the golden idol). Use SetValue(Agent, Value) to jump straight to the target, or call Complete(Agent) to skip counting entirely.

using { /Fortnite.com/Devices }
using { /Verse.org/Simulation }
using { /Verse.org/Native }

GoldenIdolTitle<localizes>(S : string) : message = "{S}"

golden_idol_handler := class(creative_device):

    @editable
    IdolPickupTrigger : trigger_device = trigger_device{}
    # Fires when the golden idol is picked up

    @editable
    QuestTracker : tracker_device = tracker_device{}

    OnBegin<override>()<suspends> : void =
        QuestTracker.SetTitleText(GoldenIdolTitle("Find the Idol"))
        QuestTracker.SetTarget(1)
        QuestTracker.AssignToAll()
        IdolPickupTrigger.TriggeredEvent.Subscribe(OnIdolPickedUp)

    OnIdolPickedUp(TriggeringAgent : ?agent) : void =
        if (A := TriggeringAgent?):
            # Option A: jump the value to the target
            QuestTracker.SetValue(A, QuestTracker.GetTarget())

            # Option B (alternative): skip counting entirely
            # QuestTracker.Complete(A)

            # Decrement the other team's tracker value as a penalty example
            # (demonstrates Decrement)
            QuestTracker.Decrement(A)

Key calls: SetValue(Agent, int), GetTarget(), Complete(Agent), Decrement(Agent).

Gotchas

1. message vs string — the #1 compile error

SetTitleText and SetDescriptionText require a message value, not a plain string. There is no StringToMessage function. Always declare a localizer helper:

MyTitle<localizes>(S : string) : message = "{S}"

Then call ObjectiveTracker.SetTitleText(MyTitle("Eliminate Guards")). Passing a raw string literal will not compile.

2. CompleteEvent sends agent, not ?agent

CompleteEvent : listenable(agent) — the handler receives a plain, already-unwrapped agent. Do not write if (A := Agent?) here; just use Agent directly. Contrast this with trigger_device.TriggeredEvent which sends ?agent and does need unwrapping.

3. IsActive[] and HasReachedTarget[] are failable — use if

Both methods carry <decides>, meaning they can fail. Always call them inside an if expression:

if (ObjectiveTracker.IsActive[A]):
    # safe to proceed

Calling them outside an if is a compile error.

4. Persistence methods are no-ops without the editor setting

Save, Load, LoadForAll, and ClearPersistence silently do nothing unless the tracker's Use Persistence property is set to Use in the device's User Options panel. Enable it in the editor first.

5. SetTarget is global, IncreaseTargetValue / DecreaseTargetValue are per-agent

SetTarget(int) changes the target for all agents at once and is clamped to 0–10 000. IncreaseTargetValue(Agent) / DecreaseTargetValue(Agent) adjust the target by 1 for a single agent. Mix them carefully or you'll accidentally reset everyone's bar.

6. AssignToAll only covers players present at call time

If a player joins mid-game, they won't automatically receive the tracker. Subscribe to a join event (e.g., from a player_spawner_device) and call Assign(Agent) for late joiners.

7. int ↔ float — no auto-conversion

Verse never silently converts between int and float. SetTarget and SetValue take int; if you compute a value as float you must convert explicitly (e.g., Int(FloatValue) if the built-in is available, or redesign the math to stay in int).