I_Persistable — Blueprint Interface

File: Content/Framework/Save/I_Persistable

⚡ C++ Status: Full Implementation — Defined in Source/PG_Framework/Public/Core/I_InterfaceLibrary.h as BlueprintNativeEvent. Do NOT create a Blueprint Interface asset. On any actor that needs save/load: Class Settings → Interfaces → Add → UPersistable. Override On Save, On Load, Get Save Tag, Needs Save. See docs/developer/cpp-integration-guide.md.

Purpose: Interface for any Actor or Component in the world that needs to save or restore per-instance state. Implemented by doors, containers, lootable objects, hidden collectibles, puzzle elements, destructibles, and any other persistent world actor.

Depends On: None Used By: SS_SaveManager, All persistent world actors

Interface Functions

Function	Inputs	Outputs	Description
`CollectState`	—	`S_WorldObjectState`	The implementer packs its current state into a generic key-value struct
`RestoreState`	StateData: `S_WorldObjectState`	—	The implementer unpacks the struct and reapplies its state
`GetPersistenceTag`	—	GameplayTag	Returns the unique gameplay tag that identifies this instance in the save manifest
`ShouldPersist`	—	Bool	Returns whether this actor should be serialised (e.g., false for temporary actors spawned via FX)
`OnPreSave`	—	—	Called before the save operation begins; used to flush transient state
`OnPostLoad`	—	—	Called after all state has been distributed; used to trigger animations, re-enable physics, etc.

Required Variable (on implementer)

Name	Type	Description
`PersistenceTag`	GameplayTag	Set in Construction Script or Defaults. Must be unique within the level. Convention: `Save.<LevelName>.<ActorClassName>.<Index>`

Implementation Pattern

flowchart LR
    A[SS_SaveManager.CollectWorldState] --> B[Iterate registered I_Persistable actors]
    B --> C[Call actor.ShouldPersist]
    C --> D{Should persist?}
    D -->|No| E[Skip]
    D -->|Yes| F[Call actor.OnPreSave]
    F --> G[Call actor.CollectState]
    G --> H[Store in WorldStateDelta map]
    H --> I[Save to disk]

    J[SS_SaveManager.DistributeWorldState] --> K[Iterate WorldStateDelta entries]
    K --> L[Find actor by ObjectTag]
    L --> M{Found?}
    M -->|No| N[Log warning]
    M -->|Yes| O[Call actor.RestoreState]
    O --> P[Call actor.OnPostLoad]
    P --> Q[Continue]

Example: BP_DoorWithState implements I_Persistable

// On CollectState
State.bDestroyed = bIsDestroyed;
State.CustomData.Add("bOpen", bIsOpen);
State.CustomData.Add("bLocked", bIsLocked);
State.CustomData.Add("Health", Health);
State.CustomData.Add("PuzzleSolved", bPuzzleSolved);
return State;

// On RestoreState(State)
bIsDestroyed = State.bDestroyed;
bIsOpen = State.CustomData["bOpen"].AsBool();
bIsLocked = State.CustomData["bLocked"].AsBool();
Health = State.CustomData["Health"].AsFloat();
bPuzzleSolved = State.CustomData["PuzzleSolved"].AsBool();

PersistenceTag Convention

Tag Pattern	Example	Used For
`Save.LevelName.ActorClass.Index`	`Save.Hospital.DoorHeavy.03`	Level-dense unique ID
`Save.Persistent.ActorName`	`Save.Persistent.MansionKey`	Unique collectibles that span levels
`Save.Global.FlagName`	`Save.Global.EndingUnlocked`	Cross-save narrative flags

Communication Matrix

Target System	Method	Why
`SS_SaveManager`	Interface call	State collection and distribution
`SS_SaveManager`	Register/Unregister	Lifecycle tracking (BeginPlay/EndPlay)

Reuse Notes

Keep CustomData entries simple: only Bool, Float, Int, String, or Name values
For complex state (arrays of structs), serialise to a Json string and store as a single CustomData entry
Use OnPostLoad to re-trigger timelines or timelines that drive animations (e.g., door opening animation after restoring closed state)
Implement ShouldPersist to return false for actors that are editor-placed but runtime-destroyed without state significance (e.g., particle emitters)
All interface functions are BlueprintImplementableEvent — no logic required in the interface itself

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