93 lines
4.4 KiB
Markdown
93 lines
4.4 KiB
Markdown
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# MapParam
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- **功能描述：** 指定一个函数为使用TMap<TKey,TValue>的函数，元素类型为通配符的泛型。
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- **使用位置：** UFUNCTION
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- **引擎模块：** Blueprint
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- **元数据类型：** string="abc"
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- **限制类型：** TMap
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- **关联项：** [MapKeyParam](MapKeyParam.md), [MapValueParam](MapValueParam.md)
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- **常用程度：** ★★★
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指定一个函数为使用TMap<TKey,TValue>的函数，元素类型为通配符的泛型。
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只能支持一个MapParam，源码中的实现是只根据一个名字来FindPin。
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在源码中，例子都是在UBlueprintMapLibrary中使用。
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## 测试代码1：
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```cpp
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UFUNCTION(BlueprintPure, CustomThunk, meta = (MapParam = "TargetMap"))
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static int32 MyMap_Count(const TMap<int32, int32>& TargetMap);
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static int32 GenericMyMap_Count(const void* TargetMap, const FMapProperty* MapProperty);
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DECLARE_FUNCTION(execMyMap_Count);
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```
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## 蓝图中效果1：
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因为只支持一个MapParam，因此如果你书写这种代码 。
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## 测试代码2：
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```cpp
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UFUNCTION(BlueprintPure, CustomThunk, meta = (MapParam = "MapA,MapB"))
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static int32 MyMap_CompareSize(const TMap<int32, int32>& MapA, const TMap<int32, int32>& MapB);
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static int32 GenericMyMap_CompareSize(void* MapA, const FMapProperty* MapAProp, void* MapB, const FMapProperty* MapBProp);
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DECLARE_FUNCTION(execMyMap_CompareSize);
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```
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会导致MapParam搜索不到Pin，从而失去通配符的功能。
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而如果要实现类似Add的功能，达到Key和Value的Pin类型也可以动态的根据Map的类型而自动的改变。则需要加上MapKeyParam 和MapValueParam 分别的指定另外的函数参数以便能找到正确的Pin，从而实现动态的根据Map类型而更改KeyValue Pin类型。MapKeyParam 和MapValueParam 指定的参数也可以为数组等容器，可以参照UBlueprintMapLibrary中的Keys和Values参数。
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```cpp
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UFUNCTION(BlueprintCallable, CustomThunk, meta = (MapParam = "TargetMap",MapKeyParam = "Key", MapValueParam = "Value"))
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static bool MyMap_FindOrAdd(const TMap<int32, int32>& TargetMap, const int32& Key, const int32& Value);
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static bool GenericMyMap_FindOrAdd(const void* TargetMap, const FMapProperty* MapProperty, const void* KeyPtr, const void* ValuePtr);
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DECLARE_FUNCTION(execMyMap_FindOrAdd);
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```
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## 蓝图中的效果2：
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## 原理代码:
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```cpp
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void UK2Node_CallFunction::ConformContainerPins()
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{
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//在这其中检测容器Pin
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const FString& MapPinMetaData = TargetFunction->GetMetaData(FBlueprintMetadata::MD_MapParam);
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const FString& MapKeyPinMetaData = TargetFunction->GetMetaData(FBlueprintMetadata::MD_MapKeyParam);
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const FString& MapValuePinMetaData = TargetFunction->GetMetaData(FBlueprintMetadata::MD_MapValueParam);
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if(!MapPinMetaData.IsEmpty() || !MapKeyPinMetaData.IsEmpty() || !MapValuePinMetaData.IsEmpty() )
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{
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// if the map pin has a connection infer from that, otherwise use the information on the key param and value param:
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bool bReadyToPropagateKeyType = false;
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FEdGraphTerminalType KeyTypeToPropagate;
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bool bReadyToPropagateValueType = false;
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FEdGraphTerminalType ValueTypeToPropagate;
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UEdGraphPin* MapPin = MapPinMetaData.IsEmpty() ? nullptr : FindPin(MapPinMetaData);
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UEdGraphPin* MapKeyPin = MapKeyPinMetaData.IsEmpty() ? nullptr : FindPin(MapKeyPinMetaData);
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UEdGraphPin* MapValuePin = MapValuePinMetaData.IsEmpty() ? nullptr : FindPin(MapValuePinMetaData);
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TryReadTypeToPropagate(MapPin, bReadyToPropagateKeyType, KeyTypeToPropagate);//读取MapPin的Key连接类型
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TryReadValueTypeToPropagate(MapPin, bReadyToPropagateValueType, ValueTypeToPropagate);//读取MapPin上连接的Map Value类型
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TryReadTypeToPropagate(MapKeyPin, bReadyToPropagateKeyType, KeyTypeToPropagate);//读取KeyPin上的连接类型
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TryReadTypeToPropagate(MapValuePin, bReadyToPropagateValueType, ValueTypeToPropagate);//读取ValuePin上的连接类型
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TryPropagateType(MapPin, KeyTypeToPropagate, bReadyToPropagateKeyType);//改变MapPin的Key当前类型
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TryPropagateType(MapKeyPin, KeyTypeToPropagate, bReadyToPropagateKeyType);//改变KeyPin的当前类型
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TryPropagateValueType(MapPin, ValueTypeToPropagate, bReadyToPropagateValueType);//改变MapPin的Value当前类型
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TryPropagateType(MapValuePin, ValueTypeToPropagate, bReadyToPropagateValueType);//改变ValuePin的当前类型
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}
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}
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```
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