ue-decomposition

name	ue-decomposition
description	Use when reviewing Unreal Engine C++ code for decomposition opportunities. UE-specific concerns — UPROPERTY chain visibility, GC rooting, unity build inlining, and UE responsibility group types. Compose with general-decomposition for universal structural checks.

UE Decomposition Domain Knowledge

UE-specific decomposition concerns that go beyond general structural analysis. These are truths about Unreal Engine's ownership model, build system, and macro conventions.

UE Responsibility Group Types

Beyond general responsibility groups (see general-decomposition), these are UE-specific seams:

• A UCLASS or USTRUCT that could live in its own header/implementation
• A group of UFUNCTION(BlueprintCallable) or UFUNCTION(Server) handlers forming a distinct API surface
• Processor/observer logic (FMassEntityQuery execution, delegate bindings) serving a different subsystem than the file's primary concern

Hand-Rolled Algorithm Replacements

Flag manual loops that replicate well-known UE library functions. Common examples:

• Manual sorted-insertion loops → Algo::LowerBoundBy + Insert
• Manual find-and-remove loops → RemoveAll, RemoveAllSwap, FindByPredicate
• Manual min/max scans → Algo::MinElementBy, Algo::MaxElementBy
• Manual copy-if → FilterByPredicate
• std::sort / std::find / std::lower_bound when Algo::* or TArray::* equivalents exist

Name the specific replacement and cite the header.

Const/Non-Const Overload Pairs

When two methods differ only in const qualification, recommend a private template helper or factoring the shared logic into a separate function. Never recommend const_cast delegation — const_cast is banned in this codebase. The C++ lint hook will block it.

Extraction Is Free

Do not withhold extraction suggestions due to perceived function-call overhead:

• Unity builds — UE amalgamates related TUs. The compiler sees callers and callees together. Small helpers inline automatically.
• FORCEINLINE — if profiling disagrees, adding it to a hot helper is trivial. Default to maximum readability.

Always propose the extraction. Never self-censor because "it might be slower."

Lifetime-Informed Decomposition

Reasons FOR splitting

• A function group operates on data it receives by reference — no pointer-ownership responsibilities. Clear parameter contract.
• A nested helper class holds no TObjectPtr<UObject> members — could be a standalone F-prefixed struct with value semantics.
• A file mixes long-lived state management (component members, cached handles) with short-lived computational helpers.

Reasons AGAINST splitting

• A class's UPROPERTY() members and the methods managing their lifetimes would end up in different files. Reviewers need the full ownership picture in one place.
• Splitting forces passing raw pointers across file boundaries where current code uses direct member access with clear ownership.
• Thread synchronisation (locks, atomics, game-thread checks) guards methods that would span multiple files. Lock scope becomes non-obvious.
• A helper captures this or member references in lambdas posted to async work. Moving it makes capture lifetime harder to audit.

When a decomposition has both arguments for and against, weigh them explicitly. If the lifetime risk outweighs the organisational benefit, do not propose the split.