Asset reference points to a Blueprint that no longer exists

Why: Some node or variable hardcoded a reference to BP_{name}, but that file was deleted or moved. The Asset Registry can't resolve it. Fix: Either: (a) re-create BP_{name} if accidentally deleted (Content Browser → right-click → Blueprint Class), or (b) update the reference to point at the correct existing Blueprint, or (c) make the reference soft (TSoftObjectPtr) so missing assets don't fail compilation.

Construct Object From Class — create UObject in BP

Blueprint-exposed version of NewObject. Cast result to your specific class.

Component pattern: create Actor Component BP for reusable logic

CREATE: New Blueprint → parent class UActorComponent (or USceneComponent if needs transform). Add variables (Health, MaxHealth). Add EventBeginPlay (available in component). Add custom events/functions (TakeDamage, Heal, OnDeath). ADD TO ACTOR: In your Actor BP → Add Component → search for your component class. Or: SpawnActorFromClass → GetComponentByClass → CastTo<BP_HealthComponent>. CROSS-COMMUNICATION: In Component's OnDeath → GetOwner → CastTo<BP_Character> → call OnCharacterDied. Or: Component has Event Dispatcher 'OnDied' → owner binds to it. BENEFIT: Reuse HealthComponent on Enemy, Player, Vehicle without code duplication.

Pressure plate trigger that activates when enough weight is on it

Pattern: BoxCollision trigger, variable OverlappingActors(int)=0. OnBeginOverlap: OverlappingActors++ → Branch(OverlappingActors >= RequiredCount) → Activate. OnEndOverlap: OverlappingActors-- → Branch(OverlappingActors < RequiredCount) → Deactivate. Use interface or event dispatcher to notify connected actors (doors, platforms).

Health and damage system with ApplyDamage and EventAnyDamage

Dealing damage: Event → ApplyDamage(TargetActor, BaseDamage, InstigatorController, DamageCauser, DamageTypeClass). Receiving: EventAnyDamage → Damage output → Subtract_FloatFloat(CurrentHealth, Damage) → FClamp(Result, 0, MaxHealth) → SET CurrentHealth → Branch(CurrentHealth <= 0) → True: DestroyActor. Initialize CurrentHealth=MaxHealth in BeginPlay.

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Create a Blueprint Actor with health variable that takes damage and destroys itself when health reaches zero

Create a Blueprint for a health pickup that restores health when overlapped by the player

Health regeneration over time with timer

Pattern: Variables RegenRate(float)=5.0, RegenDelay(float)=3.0, RegenTimerHandle. On damage received: ClearTimer(RegenTimerHandle) → SET timer(RegenDelay, RegenTick, looping=true). RegenTick function: Branch(Health < MaxHealth) → True: SET Health = FClamp(Health + RegenRate*DeltaSeconds, 0, MaxHealth). False: ClearTimer.

Pickup and collectible system with overlap trigger

Pattern: Pickup actor with SphereCollision(overlap), StaticMesh visual. OnComponentBeginOverlap → CastTo PlayerCharacter → Success: call AddScore/AddItem interface on player → PlaySoundAtLocation → SpawnEmitterAtLocation → DestroyActor(self). Set collision to OverlapOnlyPawn for performance.