这是一篇关于UE中蓝图Beginplay和C++中Beginplay
官方文档参考：Actor Lifecycle
Beginplay
One C++ Constructor > Corresponding BP Constructors > Repeat / One C++ Begin Play > Corresponding BP Begin Play
蓝图的BeginPlay是在AActor::BeginPlay()方法中被调用的
void AXXX::BeginPlay()
{
UE_LOG(LogTest, Warning, TEXT("CPP 1 Begin"));
Super::BeginPlay();
UE_LOG(LogTest, Warning, TEXT("CPP 2 Begin"));
}
那么会看到
LogTest: Warning: CPP 1 Begin
LogBlueprintUserMessages: [BP_XXX_0] Blueprint Beginplay
LogTest: Warning: CPP 2 Begin
继承于Actor的对象在调用Super::BeginPlay以后会调到AActor::BeginPlay()
void AActor::BeginPlay()
{
TRACE_OBJECT_EVENT(this, BeginPlay);
ensureMsgf(ActorHasBegunPlay == EActorBeginPlayState::BeginningPlay, TEXT("BeginPlay was called on actor %s which was in state %d"), *GetPathName(), (int32)ActorHasBegunPlay);
SetLifeSpan( InitialLifeSpan );
RegisterAllActorTickFunctions(true, false); // Components are done below.
TInlineComponentArray<UActorComponent*> Components;
GetComponents(Components);
for (UActorComponent* Component : Components)
{
// bHasBegunPlay will be true for the component if the component was renamed and moved to a new outer during initialization
if (Component->IsRegistered() && !Component->HasBegunPlay())
{
Component->RegisterAllComponentTickFunctions(true);
Component->BeginPlay();
ensureMsgf(Component->HasBegunPlay(), TEXT("Failed to route BeginPlay (%s)"), *Component->GetFullName());
}
else
{
// When an Actor begins play we expect only the not bAutoRegister false components to not be registered
//check(!Component->bAutoRegister);
}
}
if (GetAutoDestroyWhenFinished())
{
if (UWorld* MyWorld = GetWorld())
{
if (UAutoDestroySubsystem* AutoDestroySys = MyWorld->GetSubsystem<UAutoDestroySubsystem>())
{
AutoDestroySys->RegisterActor(this);
}
}
}
ReceiveBeginPlay();
ActorHasBegunPlay = EActorBeginPlayState::HasBegunPlay;
}
其中倒数第二行调用到了BlueprintImplementableEvent的方法ReceiveBeginPlay()，这个就是蓝图里的Beginplay
protected:
/** Event when play begins for this actor. */
UFUNCTION(BlueprintImplementableEvent, meta=(DisplayName = "BeginPlay"))
void ReceiveBeginPlay();
另外在调用此函数前遍历了此Actor的组件，因此组件的Beginplay会更早
void UActorComponent::BeginPlay()
{
TRACE_OBJECT_EVENT(this, BeginPlay);
check(bRegistered);
check(!bHasBegunPlay);
checkSlow(bTickFunctionsRegistered); // If this fails, someone called BeginPlay() without first calling RegisterAllComponentTickFunctions().
//CLASS_CompiledFromBlueprint：表明该类是从蓝图创建的
//CLASS_Native：Class is a native class - native interfaces will have CLASS_Native set, but not RF_MarkAsNative 与反射相关见下方 UE 反射实现分析 链接
if (GetClass()->HasAnyClassFlags(CLASS_CompiledFromBlueprint) || !GetClass()->HasAnyClassFlags(CLASS_Native))
{
ReceiveBeginPlay();
}
bHasBegunPlay = true;
}
/**
* Blueprint implementable event for when the component is beginning play, called before its owning actor's BeginPlay
* or when the component is dynamically created if the Actor has already BegunPlay.
*/
UFUNCTION(BlueprintImplementableEvent, meta=(DisplayName = "Begin Play"))
void ReceiveBeginPlay();