系列文章目录
UE蓝图 Get节点和源码
UE蓝图 Set节点和源码
UE蓝图 Cast节点和源码
UE蓝图 分支(Branch)节点和源码
UE蓝图 入口(FunctionEntry)节点和源码
UE蓝图 返回结果(FunctionResult)节点和源码
文章目录
- 系列文章目录
- 一、FunctionResult节点功能
- 二、FunctionResult节点用法
- 三、使用场景
- 四、实现过程
- 五、相关源码
一、FunctionResult节点功能
FunctionResult节点是UE蓝图中用于返回函数执行结果的重要节点之一。它可以帮助您将函数的返回值传递给调用者,并在需要时进行调试和测试。FunctionResult节点通常位于函数的末尾。
二、FunctionResult节点用法
以下是使用FunctionResult
节点的一般步骤:
- 创建FunctionResult节点:在蓝图中,定义了函数的返回参数后,FunctionResult节点会自动创建显示。
- 连接输入引脚:如果函数需要输出参数,你可以将相应的引脚连接到
FunctionResult
节点的输入引脚上。 - 使用返回值:你可以将
FunctionResult
节点的输出引脚连接到其他节点,以便基于函数的返回值执行进一步的操作。
三、使用场景
UE(Unreal Engine)的蓝图系统中的FunctionResult节点具有多种应用场景,主要涉及到需要获取函数返回值并进行进一步处理的情况。以下是一些常见的应用场景示例:
-
条件判断:
- 当你的游戏逻辑需要根据某个函数的返回值来做出决策时,可以使用FunctionResult节点来存储这个返回值,并将其连接到条件判断节点(如Branch节点)上。例如,一个函数可能返回一个布尔值来表示某个条件是否满足,你可以使用FunctionResult节点来捕获这个布尔值,并根据其值来执行不同的逻辑分支。
-
变量赋值与状态更新:
- 在游戏运行过程中,你可能需要更新某些变量的值或游戏状态。这些变量或状态可能由某个函数的返回值决定。通过FunctionResult节点,你可以获取函数的返回值,并将其赋给蓝图中的变量或用于更新游戏状态。
-
事件响应:
- 在UE中,事件是驱动游戏逻辑的重要机制。当某个事件发生时(如用户点击按钮、碰撞检测等),你可能会调用一个函数来处理这个事件,并根据函数的返回值来执行后续操作。FunctionResult节点可以帮助你捕获这些返回值,并据此作出响应。
-
数据传递与处理:
- 在复杂的游戏逻辑中,数据可能需要在不同的节点和函数之间传递。FunctionResult节点可以作为数据传递的桥梁,将一个函数的返回值传递给另一个函数或节点进行进一步处理。这种传递可以是数值、对象引用、字符串等各种数据类型。
-
异步操作:
- 在UE中,有些函数可能是异步执行的,即它们不会立即返回结果,而是在一段时间后通过回调或事件来通知结果。在这种情况下,你可以使用FunctionResult节点来等待异步操作完成并获取其结果。这通常涉及到使用延迟节点(Delay)和事件调度(Event Dispatch)来管理异步逻辑。
需要注意的是,虽然FunctionResult节点在蓝图系统中非常有用,但它只适用于能够返回值的函数。对于没有返回值的函数(返回类型为void),FunctionResult节点将不会有任何作用。此外,如果函数有多个返回值,你可能需要使用多个FunctionResult节点或者使用结构体(Struct)来封装多个返回值。
总之,FunctionResult节点在UE蓝图系统中广泛应用于条件判断、变量赋值、事件响应、数据传递和异步操作等场景,帮助开发者更加灵活地管理和处理函数的返回值。
四、实现过程
- 创建输入引脚
- 调用FKCHandler_FunctionEntry.RegisterNet注册返回值引脚
virtual void RegisterNet(FKismetFunctionContext& Context, UEdGraphPin* Net) override
{
// Do not register as a default any Pin that comes from being Split
if (Net->ParentPin == nullptr)
{
FString NetPinName = Net->PinName.ToString();
for (FBPTerminal& ResultTerm : Context.Results)
{
if ((ResultTerm.Name == NetPinName) && (ResultTerm.Type == Net->PinType))
{
Context.NetMap.Add(Net, &ResultTerm);
return;
}
}
FBPTerminal* Term = new FBPTerminal();
Context.Results.Add(Term);
Term->CopyFromPin(Net, MoveTemp(NetPinName));
Context.NetMap.Add(Net, Term);
}
}
- 调用Compile编译创建Statement
virtual void Compile(FKismetFunctionContext& Context, UEdGraphNode* Node) override
{
static const FBoolConfigValueHelper ExecutionAfterReturn(TEXT("Kismet"), TEXT("bExecutionAfterReturn"), GEngineIni);
if (ExecutionAfterReturn)
{
// for backward compatibility only
FKCHandler_VariableSet::Compile(Context, Node);
}
else
{
GenerateAssigments(Context, Node);
if (Context.IsDebuggingOrInstrumentationRequired() && Node)
{
FBlueprintCompiledStatement& TraceStatement = Context.AppendStatementForNode(Node);
TraceStatement.Type = Context.GetWireTraceType();
TraceStatement.Comment = Node->NodeComment.IsEmpty() ? Node->GetName() : Node->NodeComment;
}
// always go to return
FBlueprintCompiledStatement& GotoStatement = Context.AppendStatementForNode(Node);
GotoStatement.Type = KCST_GotoReturn;
}
}
五、相关源码
源码文件:
K2Node_FunctionResult.h
K2Node_FunctionResult.cpp
相关类:
FKCHandler_FunctionResult
K2Node_FunctionResult
class FKCHandler_FunctionResult : public FKCHandler_VariableSet
{
public:
FKCHandler_FunctionResult(FKismetCompilerContext& InCompilerContext)
: FKCHandler_VariableSet(InCompilerContext)
{
}
virtual void RegisterNet(FKismetFunctionContext& Context, UEdGraphPin* Net) override
{
// Do not register as a default any Pin that comes from being Split
if (Net->ParentPin == nullptr)
{
FString NetPinName = Net->PinName.ToString();
for (FBPTerminal& ResultTerm : Context.Results)
{
if ((ResultTerm.Name == NetPinName) && (ResultTerm.Type == Net->PinType))
{
Context.NetMap.Add(Net, &ResultTerm);
return;
}
}
FBPTerminal* Term = new FBPTerminal();
Context.Results.Add(Term);
Term->CopyFromPin(Net, MoveTemp(NetPinName));
Context.NetMap.Add(Net, Term);
}
}
virtual void Compile(FKismetFunctionContext& Context, UEdGraphNode* Node) override
{
static const FBoolConfigValueHelper ExecutionAfterReturn(TEXT("Kismet"), TEXT("bExecutionAfterReturn"), GEngineIni);
if (ExecutionAfterReturn)
{
// for backward compatibility only
FKCHandler_VariableSet::Compile(Context, Node);
}
else
{
GenerateAssigments(Context, Node);
if (Context.IsDebuggingOrInstrumentationRequired() && Node)
{
FBlueprintCompiledStatement& TraceStatement = Context.AppendStatementForNode(Node);
TraceStatement.Type = Context.GetWireTraceType();
TraceStatement.Comment = Node->NodeComment.IsEmpty() ? Node->GetName() : Node->NodeComment;
}
// always go to return
FBlueprintCompiledStatement& GotoStatement = Context.AppendStatementForNode(Node);
GotoStatement.Type = KCST_GotoReturn;
}
}
virtual bool RequiresRegisterNetsBeforeScheduling() const override
{
return true;
}
};
#if WITH_EDITORONLY_DATA
namespace
{
void GatherFunctionResultNodeForLocalization(const UObject* const Object, FPropertyLocalizationDataGatherer& PropertyLocalizationDataGatherer, const EPropertyLocalizationGathererTextFlags GatherTextFlags)
{
const UK2Node_FunctionResult* const FunctionResultNode = CastChecked<UK2Node_FunctionResult>(Object);
// Function Result (aka, Return) nodes always report their values as being the default
// but we still need to gather them as they are the only place the values are defined
const FString PathToObject = FunctionResultNode->GetPathName();
for (const UEdGraphPin* Pin : FunctionResultNode->Pins)
{
if (!Pin->DefaultTextValue.IsEmpty())
{
PropertyLocalizationDataGatherer.GatherTextInstance(Pin->DefaultTextValue, FString::Printf(TEXT("%s.%s"), *PathToObject, *Pin->GetName()), /*bIsEditorOnly*/true);
}
}
PropertyLocalizationDataGatherer.GatherLocalizationDataFromObject(FunctionResultNode, GatherTextFlags);
}
}
#endif
UK2Node_FunctionResult::UK2Node_FunctionResult(const FObjectInitializer& ObjectInitializer)
: Super(ObjectInitializer)
{
#if WITH_EDITORONLY_DATA
{ static const FAutoRegisterLocalizationDataGatheringCallback AutomaticRegistrationOfLocalizationGatherer(UK2Node_FunctionResult::StaticClass(), &GatherFunctionResultNodeForLocalization); }
#endif
}
FText UK2Node_FunctionResult::GetNodeTitle(ENodeTitleType::Type TitleType) const
{
if (ENodeTitleType::MenuTitle == TitleType)
{
return NSLOCTEXT("K2Node", "ReturnNodeMenuTitle", "Add Return Node...");
}
return NSLOCTEXT("K2Node", "ReturnNode", "Return Node");
}
void UK2Node_FunctionResult::AllocateDefaultPins()
{
CreatePin(EGPD_Input, UEdGraphSchema_K2::PC_Exec, UEdGraphSchema_K2::PN_Execute);
if (UFunction* const Function = FunctionReference.ResolveMember<UFunction>(GetBlueprintClassFromNode()))
{
CreatePinsForFunctionEntryExit(Function, /*bIsFunctionEntry=*/ false);
}
Super::AllocateDefaultPins();
FFillDefaultPinValueHelper::FillAll(this);
}
bool UK2Node_FunctionResult::CanCreateUserDefinedPin(const FEdGraphPinType& InPinType, EEdGraphPinDirection InDesiredDirection, FText& OutErrorMessage)
{
bool bResult = Super::CanCreateUserDefinedPin(InPinType, InDesiredDirection, OutErrorMessage);
if (bResult)
{
if(InDesiredDirection == EGPD_Output)
{
OutErrorMessage = NSLOCTEXT("K2Node", "AddOutputPinError", "Cannot add output pins to function result node!");
bResult = false;
}
}
return bResult;
}
UEdGraphPin* UK2Node_FunctionResult::CreatePinFromUserDefinition(const TSharedPtr<FUserPinInfo> NewPinInfo)
{
UEdGraphPin* Pin = CreatePin(EGPD_Input, NewPinInfo->PinType, NewPinInfo->PinName);
CastChecked<UEdGraphSchema_K2>(GetSchema())->SetPinAutogeneratedDefaultValue(Pin, NewPinInfo->PinDefaultValue);
return Pin;
}
void UK2Node_FunctionResult::FixupPinStringDataReferences(FArchive* SavingArchive)
{
Super::FixupPinStringDataReferences(SavingArchive);
if (SavingArchive)
{
UpdateUserDefinedPinDefaultValues();
}
}
FNodeHandlingFunctor* UK2Node_FunctionResult::CreateNodeHandler(FKismetCompilerContext& CompilerContext) const
{
return new FKCHandler_FunctionResult(CompilerContext);
}
FText UK2Node_FunctionResult::GetTooltipText() const
{
return NSLOCTEXT("K2Node", "ReturnNodeTooltip", "The node terminates the function's execution. It returns output parameters.");
}
void UK2Node_FunctionResult::GetMenuActions(FBlueprintActionDatabaseRegistrar& ActionRegistrar) const
{
// actions get registered under specific object-keys; the idea is that
// actions might have to be updated (or deleted) if their object-key is
// mutated (or removed)... here we use the node's class (so if the node
// type disappears, then the action should go with it)
UClass* ActionKey = GetClass();
// to keep from needlessly instantiating a UBlueprintNodeSpawner, first
// check to make sure that the registrar is looking for actions of this type
// (could be regenerating actions for a specific asset, and therefore the
// registrar would only accept actions corresponding to that asset)
if (ActionRegistrar.IsOpenForRegistration(ActionKey))
{
UBlueprintNodeSpawner* NodeSpawner = UBlueprintNodeSpawner::Create(GetClass());
check(NodeSpawner != nullptr);
ActionRegistrar.AddBlueprintAction(ActionKey, NodeSpawner);
}
}
bool UK2Node_FunctionResult::IsCompatibleWithGraph(UEdGraph const* Graph) const
{
auto K2Schema = Cast<const UEdGraphSchema_K2>(Graph ? Graph->GetSchema() : nullptr);
const bool bIsConstructionScript = (K2Schema != nullptr) ? K2Schema->IsConstructionScript(Graph) : false;
const bool bIsCompatible = (K2Schema != nullptr) ? (EGraphType::GT_Function == K2Schema->GetGraphType(Graph)) : false;
return bIsCompatible && !bIsConstructionScript && Super::IsCompatibleWithGraph(Graph);
}
TArray<UK2Node_FunctionResult*> UK2Node_FunctionResult::GetAllResultNodes() const
{
TArray<UK2Node_FunctionResult*> AllResultNodes;
if (auto Graph = GetGraph())
{
Graph->GetNodesOfClass(AllResultNodes);
}
return AllResultNodes;
}
void UK2Node_FunctionResult::PostPlacedNewNode()
{
Super::PostPlacedNewNode();
// adhere to the function's inherited signature (if there is one)
SyncWithEntryNode();
// reflect any user added outputs (tracked by pre-existing result nodes)
SyncWithPrimaryResultNode();
}
void UK2Node_FunctionResult::PostPasteNode()
{
Super::PostPasteNode();
// adhere to the function's inherited signature (if there is one)
SyncWithEntryNode();
// reflect any user added outputs (tracked by pre-existing result nodes)
SyncWithPrimaryResultNode();
// reflect editability of node in pins
MakePinsEditable();
}
bool UK2Node_FunctionResult::CanUserDeleteNode() const
{
bool bCanDelete = true;
if (!bIsEditable)
{
if (UEdGraph* Graph = GetGraph())
{
bCanDelete = false;
for (UEdGraphNode* Node : Graph->Nodes)
{
UK2Node_FunctionResult* ResultNode = Cast<UK2Node_FunctionResult>(Node);
if (ResultNode && ResultNode != this)
{
bCanDelete = true;
break;
}
}
}
}
return bCanDelete;
}
void UK2Node_FunctionResult::SyncWithEntryNode()
{
bool bWasSignatureMismatched = false;
if (UEdGraph* Graph = GetGraph())
{
for (UEdGraphNode* Node : Graph->Nodes)
{
if (UK2Node_FunctionEntry* EntryNode = Cast<UK2Node_FunctionEntry>(Node))
{
bWasSignatureMismatched = !EntryNode->FunctionReference.IsSameReference(FunctionReference) || (!EntryNode->bIsEditable && UserDefinedPins.Num() > 0);
// If the entry is editable, so is the result
bIsEditable = EntryNode->bIsEditable;
FunctionReference = EntryNode->FunctionReference;
break;
}
}
}
if (bWasSignatureMismatched)
{
// to handle pasting of a result node from one function into another;
// if the new function is not editable (like for one that is overidden),
// then we shouldn't have userdefined pins
if (!bIsEditable)
{
// iterate backwards so we can remove items from the list as we go
for (int32 UserPinIndex = UserDefinedPins.Num() - 1; UserPinIndex >= 0; --UserPinIndex)
{
RemoveUserDefinedPin(UserDefinedPins[UserPinIndex]);
}
}
ReconstructNode();
}
}
void UK2Node_FunctionResult::SyncWithPrimaryResultNode()
{
UK2Node_FunctionResult* PrimaryNode = nullptr;
TArray<UK2Node_FunctionResult*> AllResultNodes = GetAllResultNodes();
for (auto ResultNode : AllResultNodes)
{
if (ResultNode && (this != ResultNode))
{
PrimaryNode = ResultNode;
break;
}
}
if (PrimaryNode)
{
FunctionReference = PrimaryNode->FunctionReference;
bIsEditable = PrimaryNode->bIsEditable;
// Temporary array that will contain our list of Old Pins that are no longer part of the return signature
TArray< TSharedPtr<FUserPinInfo> > OldPins = UserDefinedPins;
// Temporary array that will contain our list of Signature Pins that need to be added
TArray< TSharedPtr<FUserPinInfo> > SignaturePins = PrimaryNode->UserDefinedPins;
for (int OldIndex = OldPins.Num() - 1; OldIndex >= 0; --OldIndex)
{
TSharedPtr<FUserPinInfo> OldPin = OldPins[OldIndex];
if (!OldPin.IsValid())
{
OldPins.RemoveAt(OldIndex);
}
else
{
for (int SignatureIndex = SignaturePins.Num() - 1; SignatureIndex >= 0; --SignatureIndex)
{
TSharedPtr<FUserPinInfo> SignaturePin = SignaturePins[SignatureIndex];
if (!SignaturePin.IsValid())
{
SignaturePins.RemoveAt(SignatureIndex);
}
else if (OldPin->PinName == SignaturePin->PinName &&
OldPin->PinType == SignaturePin->PinType &&
OldPin->DesiredPinDirection == SignaturePin->DesiredPinDirection)
{
// We have a match between our Signature pins and our Old Pins,
// so we can leave the old pin as is by removing it from both temporary lists.
OldPins.RemoveAt(OldIndex);
SignaturePins.RemoveAt(SignatureIndex);
break;
}
}
}
}
// Remove old pins that are not part of the primary node signature
for (TSharedPtr<FUserPinInfo> OldPinToRemove : OldPins)
{
RemoveUserDefinedPin(OldPinToRemove);
}
// Add pins that don't exist yet but are part of the primary node signature
for (TSharedPtr<FUserPinInfo> SignaturePinToAdd : SignaturePins)
{
TSharedPtr<FUserPinInfo> NewPinInfo = MakeShareable(new FUserPinInfo());
NewPinInfo->PinName = SignaturePinToAdd->PinName;
NewPinInfo->PinType = SignaturePinToAdd->PinType;
NewPinInfo->DesiredPinDirection = SignaturePinToAdd->DesiredPinDirection;
UserDefinedPins.Add(NewPinInfo);
}
ReconstructNode();
}
}
void UK2Node_FunctionResult::MakePinsEditable()
{
// only do this step if this node is editable
if (IsEditable())
{
// for each pin, excluding the 'exec' pin
for (int PinIdx = 1; PinIdx < Pins.Num(); ++PinIdx)
{
UEdGraphPin* Pin = Pins[PinIdx];
if (!UserDefinedPinExists(Pin->GetFName()))
{
UserDefinedPins.Add(MakeShared<FUserPinInfo>(*Pin));
}
}
}
}
void UK2Node_FunctionResult::ValidateNodeDuringCompilation(class FCompilerResultsLog& MessageLog) const
{
Super::ValidateNodeDuringCompilation(MessageLog);
auto AllResultNodes = GetAllResultNodes();
UK2Node_FunctionResult* OtherResult = AllResultNodes.Num() ? AllResultNodes[0] : nullptr;
if (OtherResult && (OtherResult != this))
{
for (auto Pin : Pins)
{
auto OtherPin = OtherResult->FindPin(Pin->PinName);
if (!OtherPin || (OtherPin->PinType != Pin->PinType))
{
MessageLog.Error(*NSLOCTEXT("K2Node", "FunctionResult_DifferentReturnError", "Return nodes don't match each other: @@, @@").ToString(), this, OtherResult);
break;
}
}
}
}