vault backup: 2024-10-12 17:19:45
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# ScriptOperator
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- **功能描述：** 把第一个参数为结构的静态函数包装成结构的运算符。
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- **使用位置：** UFUNCTION
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- **引擎模块：** Script
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- **元数据类型：** string="a;b;c"
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- **常用程度：** ★★★
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把第一个参数为结构的静态函数包装成结构的运算符。
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- 可以包含多个运算符。
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不同的运算符需要匹配不同的函数签名。规则见如下：
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- bool运算符：bool
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- bool FuncName(const FMyStruct& Value); //Value的类型可以是const FMyStruct&或者直接FMyStruct
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- 一元运算符：neg (取负)
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- FMyStruct FuncName(const FMyStruct&);
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- 比较运算符： (==, !=, <, <=, >, >=)
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- bool FuncName(const FMyStruct, OtherType); //OtherType可以是其他任何类型
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- 数学运算符： (+, -, *, /, %, &, |, ^, >>, <<)
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- ReturnType FuncName(const FMyStruct&, OtherType); //ReturnType 和 OtherType可以是其他任何类型
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- 数学赋值运算符：(+=, -=, *=, /=, %=, &=, |=, ^=, >>=, <<=)
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- FMyStruct FuncName(const FMyStruct&, OtherType); //OtherType可以是其他任何类型
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可见，如果想一个函数同时支持普通数学运算符和赋值运算符，函数签名可以是：
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FMyStruct FuncName(const FMyStruct&, OtherType); //这里OtherType可以是任何类型，也可以是FMyStruct
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这个也常常一起配合ScriptMethod使用，这样就可以在结构中一起提供一个运算成员函数，这个函数的名字还可以通过ScriptMethod来自定义。
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源码里也常见到和ScriptMethodSelfReturn使用的例子，如+=运算符上。但其实ScriptMethodSelfReturn不是必须的，在+=的时候，自然会把返回值应用到第一个参数上。
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## 测试代码：
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```cpp
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USTRUCT(BlueprintType)
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struct INSIDER_API FMyPythonMathStruct
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{
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GENERATED_BODY()
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public:
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UPROPERTY(BlueprintReadWrite, EditAnywhere)
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int32 Value = 0;
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};
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UCLASS(Blueprintable, BlueprintType)
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class INSIDER_API UMyPython_Operator_Test :public UObject
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{
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GENERATED_BODY()
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public:
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UFUNCTION(BlueprintCallable, meta = (ScriptMethod=HasValue,ScriptOperator = "bool"))
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static bool IsValid(const FMyPythonMathStruct& InStruct) { return InStruct.Value != 0; }
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UFUNCTION(BlueprintCallable, meta = (ScriptOperator = "neg"))
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static FMyPythonMathStruct Neg(const FMyPythonMathStruct& InStruct) { return { -InStruct.Value }; }
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UFUNCTION(BlueprintCallable, meta = (ScriptOperator = "=="))
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static bool IsEqual(const FMyPythonMathStruct& A, const FMyPythonMathStruct& B) { return A.Value == B.Value; }
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UFUNCTION(BlueprintCallable, meta = (ScriptOperator = "+;+="))
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static FMyPythonMathStruct AddInt(FMyPythonMathStruct InStruct, const int32 InValue) { InStruct.Value += InValue; return InStruct; }
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};
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```
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## 生成的py代码：
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可见，在py里生成了__bool__，__eq__，__add__，__iadd__，__neg__的函数。同时IsValid加上了ScriptMethod，就有了另一个has_value函数。
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```cpp
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class MyPythonMathStruct(StructBase):
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r"""
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My Python Math Struct
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**C++ Source:**
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- **Module**: Insider
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- **File**: MyPython_ScriptOperator.h
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**Editor Properties:** (see get_editor_property/set_editor_property)
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- ``value`` (int32): [Read-Write]
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"""
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def __init__(self, value: int = 0) -> None:
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...
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@property
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def value(self) -> int:
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r"""
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(int32): [Read-Write]
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"""
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...
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@value.setter
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def value(self, value: int) -> None:
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...
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def has_value(self) -> bool:
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r"""
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x.has_value() -> bool
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Is Valid
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Returns:
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bool:
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"""
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...
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def __bool__(self) -> bool:
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r"""
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Is Valid
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"""
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...
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def __eq__(self, other: object) -> bool:
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r"""
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**Overloads:**
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- ``MyPythonMathStruct`` Is Equal
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"""
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...
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def __add__(self, other: MyPythonMathStruct) -> None:
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r"""
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**Overloads:**
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- ``int32`` Add Int
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"""
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...
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def __iadd__(self, other: MyPythonMathStruct) -> None:
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r"""
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**Overloads:**
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- ``int32`` Add Int
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"""
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...
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def __neg__(self) -> None:
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r"""
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Neg
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"""
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...
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```
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## 进行运行的测试：
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可见确实支持了数学+=运算符和bool的比较。
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```cpp
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LogPython: a=unreal.MyPythonMathStruct(3)
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LogPython: print(a)
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LogPython: <Struct 'MyPythonMathStruct' (0x0000074C90D5DCF0) {value: 3}>
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LogPython: print(not a)
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LogPython: False
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LogPython: a+=3
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LogPython: print(a)
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LogPython: <Struct 'MyPythonMathStruct' (0x0000074C90D5DCF0) {value: 6}>
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LogPython: print(-a)
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LogPython: <Struct 'MyPythonMathStruct' (0x0000074C90D5DCF0) {value: -6}>
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```
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## 原理：
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具体的包装函数都在GenerateWrappedOperator 里，具体想了解的可细看这里。
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```cpp
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auto GenerateWrappedOperator = [this, &OutGeneratedWrappedTypeReferences, &OutDirtyModules](const UFunction* InFunc, const PyGenUtil::FGeneratedWrappedMethod& InTypeMethod)
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{
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// Only static functions can be hoisted onto other types
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if (!InFunc->HasAnyFunctionFlags(FUNC_Static))
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{
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REPORT_PYTHON_GENERATION_ISSUE(Error, TEXT("Non-static function '%s.%s' is marked as 'ScriptOperator' but only static functions can be hoisted."), *InFunc->GetOwnerClass()->GetName(), *InFunc->GetName());
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return;
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}
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// Get the list of operators to apply this function to
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TArray<FString> ScriptOperators;
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{
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const FString& ScriptOperatorsStr = InFunc->GetMetaData(PyGenUtil::ScriptOperatorMetaDataKey);
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ScriptOperatorsStr.ParseIntoArray(ScriptOperators, TEXT(";"));
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}
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// Go through and try and create a function for each operator, validating that the signature matches what the operator expects
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for (const FString& ScriptOperator : ScriptOperators)
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{
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PyGenUtil::FGeneratedWrappedOperatorSignature OpSignature;
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if (!PyGenUtil::FGeneratedWrappedOperatorSignature::StringToSignature(*ScriptOperator, OpSignature))
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{
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REPORT_PYTHON_GENERATION_ISSUE(Error, TEXT("Function '%s.%s' is marked as 'ScriptOperator' but uses an unknown operator type '%s'."), *InFunc->GetOwnerClass()->GetName(), *InFunc->GetName(), *ScriptOperator);
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continue;
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}
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PyGenUtil::FGeneratedWrappedOperatorFunction OpFunc;
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{
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FString SignatureError;
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if (!OpFunc.SetFunction(InTypeMethod.MethodFunc, OpSignature, &SignatureError))
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{
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REPORT_PYTHON_GENERATION_ISSUE(Error, TEXT("Function '%s.%s' is marked as 'ScriptOperator' but has an invalid signature for the '%s' operator: %s."), *InFunc->GetOwnerClass()->GetName(), *InFunc->GetName(), *ScriptOperator, *SignatureError);
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continue;
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}
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}
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// Ensure that we've generated a finalized Python type for this struct since we'll be adding this function as a operator on that type
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const UScriptStruct* HostedStruct = CastFieldChecked<const FStructProperty>(OpFunc.SelfParam.ParamProp)->Struct;
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if (GenerateWrappedStructType(HostedStruct, OutGeneratedWrappedTypeReferences, OutDirtyModules, EPyTypeGenerationFlags::ForceShouldExport))
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{
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// Find the wrapped type for the struct as that's what we'll actually add the operator to (via its meta-data)
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TSharedPtr<PyGenUtil::FGeneratedWrappedStructType> HostedStructGeneratedWrappedType = StaticCastSharedPtr<PyGenUtil::FGeneratedWrappedStructType>(GeneratedWrappedTypes.FindRef(PyGenUtil::GetTypeRegistryName(HostedStruct)));
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check(HostedStructGeneratedWrappedType.IsValid());
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StaticCastSharedPtr<FPyWrapperStructMetaData>(HostedStructGeneratedWrappedType->MetaData)->OpStacks[(int32)OpSignature.OpType].Funcs.Add(MoveTemp(OpFunc));
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}
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}
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};
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```
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