105 lines
4.2 KiB
Markdown
105 lines
4.2 KiB
Markdown
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# DataTablePin
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- **功能描述：** 指定一个函数参数为DataTable或CurveTable类型，以便为FName的其他参数提供RowNameList的选择。
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- **使用位置：** UFUNCTION
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- **引擎模块：** Pin
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- **元数据类型：** string="abc"
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- **限制类型：** DataTable，CurveTable
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- **常用程度：** ★★
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指定一个函数参数为UDataTable类型，这样就可以加载根据DataTable里的数据，为RowName提供一个List来选择，而不是手填。支持的类型是DataTable和CurveTable
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如果是DataTablePin，则会采用UK2Node_CallDataTableFunction来生成蓝图节点，以便在DataTable Pin连接参数改变的时候，触发RowNameList的刷新。
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UK2Node_GetDataTableRow也是一个单独的蓝图节点。
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但是发现RowName并没有用meta指定？但是有判断函数的参数如果类型是FName，就会把它当作RowName来看待。（这么简单粗糙的判断，也是因为其并不打算把这个Meta给用户使用）。因此实际上函数里可以有多个FName的参数，都会被自动的赋予RowNameList
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在源码中用的地方只有UDataTableFunctionLibrary
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```cpp
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UFUNCTION(BlueprintCallable, Category = "DataTable", meta = (ExpandEnumAsExecs="OutResult", DataTablePin="CurveTable"))
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static ENGINE_API void EvaluateCurveTableRow(UCurveTable* CurveTable, FName RowName, float InXY, TEnumAsByte<EEvaluateCurveTableResult::Type>& OutResult, float& OutXY,const FString& ContextString);
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```
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## 测试代码：
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```cpp
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UFUNCTION(BlueprintCallable, meta = (DataTablePin="CurveTable"))
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static void GetMyCurveTableRow(UCurveTable* CurveTable, FName MyRowName, float InXY, float& OutXY,const FString& ContextString){}
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UFUNCTION(BlueprintCallable, meta = (DataTablePin="TargetTable"))
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static bool HasMyDataTableRow(UDataTable* TargetTable, FName MyRowName,FName OtherRowName){return false;}
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```
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## 蓝图效果：
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左侧为自己定义的函数节点，可以看见左侧的蓝图节点上的Name都变成了CurveTable和DataTable里的RowNameList，即使这些FName参数并没有什么特殊指定，但是蓝图系统里自动识别到FName类型并改变了实际的Pin Widget.
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## 原理：
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如果发现FName节点，会去尝试找DataTablePin，然后根据DataTablePin的类型来改变FName类型的Pin类型。
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```cpp
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TSharedPtr<class SGraphPin> FBlueprintGraphPanelPinFactory::CreatePin(class UEdGraphPin* InPin) const
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{
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if (InPin->PinType.PinCategory == UEdGraphSchema_K2::PC_Name)
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{
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UObject* Outer = InPin->GetOuter();
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// Create drop down combo boxes for DataTable and CurveTable RowName pins
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const UEdGraphPin* DataTablePin = nullptr;
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if (Outer->IsA(UK2Node_CallFunction::StaticClass()))
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{
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const UK2Node_CallFunction* CallFunctionNode = CastChecked<UK2Node_CallFunction>(Outer);
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if (CallFunctionNode)
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{
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const UFunction* FunctionToCall = CallFunctionNode->GetTargetFunction();
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if (FunctionToCall)
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{
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const FString& DataTablePinName = FunctionToCall->GetMetaData(FBlueprintMetadata::MD_DataTablePin);
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DataTablePin = CallFunctionNode->FindPin(DataTablePinName);
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}
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}
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}
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else if (Outer->IsA(UK2Node_GetDataTableRow::StaticClass()))
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{
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const UK2Node_GetDataTableRow* GetDataTableRowNode = CastChecked<UK2Node_GetDataTableRow>(Outer);
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DataTablePin = GetDataTableRowNode->GetDataTablePin();
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}
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if (DataTablePin)
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{
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if (DataTablePin->DefaultObject != nullptr && DataTablePin->LinkedTo.Num() == 0)
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{
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if (auto DataTable = Cast<UDataTable>(DataTablePin->DefaultObject))
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{
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return SNew(SGraphPinDataTableRowName, InPin, DataTable);
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}
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if (DataTablePin->DefaultObject->IsA(UCurveTable::StaticClass()))
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{
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UCurveTable* CurveTable = (UCurveTable*)DataTablePin->DefaultObject;
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if (CurveTable)
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{
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TArray<TSharedPtr<FName>> RowNames;
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/** Extract all the row names from the RowMap */
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for (TMap<FName, FRealCurve*>::TConstIterator Iterator(CurveTable->GetRowMap()); Iterator; ++Iterator)
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{
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/** Create a simple array of the row names */
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TSharedPtr<FName> RowNameItem = MakeShareable(new FName(Iterator.Key()));
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RowNames.Add(RowNameItem);
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}
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return SNew(SGraphPinNameList, InPin, RowNames);
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}
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}
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}
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}
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}
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return nullptr;
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}
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```
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