Unreal Engine虚幻引擎避坑

Garbage Collection

• - Raw pointers to UObjects get garbage collected — use UPROPERTY() to prevent
• INLINECODE1 marks for GC tracking — without it, pointer becomes dangling
• INLINECODE2 for optional references — doesn't prevent collection, check INLINECODE3
• INLINECODE4 for UObjects — never raw new, GC won't track it

UPROPERTY and UFUNCTION

• - UPROPERTY() required for Blueprint access — and for GC tracking
• INLINECODE7 for Blueprint callable/events — also required for replication
• INLINECODE8 vs VisibleAnywhere — edit allows changes, visible is read-only
• INLINECODE10 vs BlueprintReadOnly — controls Blueprint access level

Actor Lifecycle

• - BeginPlay after all components initialized — safe to access components
• Constructor runs on CDO (Class Default Object) — don't spawn actors or access world
• INLINECODE13 before BeginPlay — for component setup
• INLINECODE14 for cleanup — called on destroy and level transition

Tick Performance

• - Disable tick when not needed — INLINECODE15
• Use timers instead of tick + counter — INLINECODE16
• Tick groups for ordering — PrePhysics, DuringPhysics, INLINECODE19
• Blueprint tick expensive — move hot logic to C++

Replication

• - Server is authority — clients request, server validates and replicates
• INLINECODE20 for variable sync — implement INLINECODE21
• INLINECODE22 for client-to-server RPC — must be Reliable or INLINECODE24
• INLINECODE25 to check if server — before executing authoritative logic
• INLINECODE26 and RemoteRole for network role checks — ROLE_Authority is server

Asset References

• - Hard references load with parent — bloats memory, use for always-needed
• Soft references (TSoftObjectPtr) load on demand — for optional or large assets
• INLINECODE30 or AsyncLoad for soft refs — don't access until loaded
• Blueprint class references: TSubclassOf<T> — type-safe class selection

Memory and Pointers

• - TSharedPtr for non-UObjects — reference counted, auto-deletes
• INLINECODE34 for exclusive ownership — can't copy, moves only
• INLINECODE35 for creation — single allocation for object and control block
• Never mix raw new/delete with smart pointers — choose one pattern

Common Mistakes

• - Accessing null actor in Blueprint — use IsValid() node before access
• PIE (Play In Editor) vs packaged build differ — test shipping build
• Hot reload corrupts Blueprints — close editor, build, reopen
• INLINECODE38 null in constructor — world doesn't exist yet, use BeginPlay
• Spawning in constructor crashes — defer to BeginPlay or later
• INLINECODE39 for display, FName for identifiers — FName is hashed, faster comparison