174 lines
6.1 KiB
Markdown
174 lines
6.1 KiB
Markdown
# ScriptDefaultMake
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- **功能描述：** 禁用结构上的HasNativeMake，在脚本里构造的时候不调用C++里的NativeMake函数，而采用脚本内建的默认初始化方式。
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- **使用位置：** USTRUCT
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- **引擎模块：** Script
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- **元数据类型：** bool
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- **关联项：** [ScriptDefaultBreak](ScriptDefaultBreak.md)
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- **常用程度：** ★
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禁用结构上的HasNativeMake，在脚本里构造的时候不调用C++里的NativeMake函数，而采用脚本内建的默认初始化方式。
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ScriptDefaultBreak也是同理。
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## 测试代码：
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```cpp
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USTRUCT(BlueprintType, meta = (ScriptDefaultMake, ScriptDefaultBreak,HasNativeMake = "/Script/Insider.MyPython_MakeBreak_Test.MyNativeMake", HasNativeBreak = "/Script/Insider.MyPython_MakeBreak_Test.MyNativeBreak"))
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struct INSIDER_API FMyPythonMBStructNative
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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 MyInt = 0;
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UPROPERTY(BlueprintReadWrite, EditAnywhere)
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FString MyString;
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};
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UCLASS(Blueprintable, BlueprintType)
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class INSIDER_API UMyPython_MakeBreak_Test :public UObject
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{
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GENERATED_BODY()
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public:
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UFUNCTION(BlueprintPure, meta = ())
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static FMyPythonMBStructNative MyNativeMake(int32 InInt) { return FMyPythonMBStructNative{ InInt,TEXT("Hello") }; }
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UFUNCTION(BlueprintPure, meta = ())
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static void MyNativeBreak(const FMyPythonMBStructNative& InStruct, int& outInt) { outInt = InStruct.MyInt + 123; }
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};
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```
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## 生成的py代码：
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无论有没有加ScriptDefaultMake, ScriptDefaultBreak，MyPythonMBStructNative生成的py代码其实是一样的。不同点在于构成和to_tuple时候的结果不同。
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```cpp
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class MyPythonMBStructNative(StructBase):
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r"""
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My Python MBStruct Native
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**C++ Source:**
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- **Module**: Insider
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- **File**: MyPython_ScriptMakeBreak.h
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**Editor Properties:** (see get_editor_property/set_editor_property)
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- ``my_int`` (int32): [Read-Write]
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- ``my_string`` (str): [Read-Write]
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"""
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def __init__(self, int: int = 0) -> None:
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...
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@property
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def my_int(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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@my_int.setter
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def my_int(self, value: int) -> None:
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...
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@property
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def my_string(self) -> str:
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r"""
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(str): [Read-Write]
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"""
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...
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@my_string.setter
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def my_string(self, value: str) -> None:
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...
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```
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## 运行的结果：
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- 第二段是加了ScriptDefaultMake, ScriptDefaultBreak后的效果。我故意在C++的Make和Break函数里做了一些不一样，可以观察到调用到C++里的函数。
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- 第一段是在代码里加上ScriptDefaultMake, ScriptDefaultBreak后（保留HasNativeMake，HasNativeBreak）调用的结果，可见C++里的Make/Break函数就没有再被调用到了。
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```cpp
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LogPython: b=unreal.MyPythonMBStructNative()
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LogPython: print(b)
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LogPython: <Struct 'MyPythonMBStructNative' (0x0000085F2EE9E680) {my_int: 0, my_string: "Hello"}>
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LogPython: print(b.to_tuple())
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LogPython: (123,)
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LogPython: b=unreal.MyPythonMBStructNative()
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LogPython: print(b)
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LogPython: <Struct 'MyPythonMBStructNative' (0x000005E6C3AAFDC0) {my_int: 0, my_string: ""}>
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LogPython: print(b.to_tuple())
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LogPython: (0, '')
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```
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## 原理：
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在FindMakeBreakFunction函数里，如果发现有ScriptDefaultMake或ScriptDefaultBreak标记，就不去使用C++里由HasNativeMake，HasNativeBreak指定的函数。
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另外py里的结构初始化会调用到默认的init或者结构的make函数，而to_tuple就相当于break的作用，会调用到默认的每个属性to_tuple或者是结构的自定义break函数。
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```cpp
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const FName ScriptDefaultMakeMetaDataKey = TEXT("ScriptDefaultMake");
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const FName ScriptDefaultBreakMetaDataKey = TEXT("ScriptDefaultBreak");
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namespace UE::Python
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{
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/**
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* Finds the UFunction corresponding to the name specified by 'HasNativeMake' or 'HasNativeBreak' meta data key.
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* @param The structure to inspect for the 'HasNativeMake' or 'HasNativeBreak' meta data keys.
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* @param InNativeMetaDataKey The native meta data key name. Can only be 'HasNativeMake' or 'HasNativeBreak'.
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* @param InScriptDefaultMetaDataKey The script default meta data key name. Can only be 'ScriptDefaultMake' or 'ScriptDefaultBreak'.
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* @param NotFoundFn Function invoked if the structure specifies as Make or Break function, but the function couldn't be found.
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* @return The function, if the struct has the meta key and if the function was found. Null otherwise.
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*/
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template<typename NotFoundFuncT>
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UFunction* FindMakeBreakFunction(const UScriptStruct* InStruct, const FName& InNativeMetaDataKey, const FName& InScriptDefaultMetaDataKey, const NotFoundFuncT& NotFoundFn)
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{
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check(InNativeMetaDataKey == PyGenUtil::HasNativeMakeMetaDataKey || InNativeMetaDataKey == PyGenUtil::HasNativeBreakMetaDataKey);
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check(InScriptDefaultMetaDataKey == PyGenUtil::ScriptDefaultMakeMetaDataKey || InScriptDefaultMetaDataKey == PyGenUtil::ScriptDefaultBreakMetaDataKey);
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UFunction* MakeBreakFunc = nullptr;
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if (!InStruct->HasMetaData(InScriptDefaultMetaDataKey)) // <--- 有了default, 会直接返回null
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{
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const FString MakeBreakFunctionName = InStruct->GetMetaData(InNativeMetaDataKey);
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if (!MakeBreakFunctionName.IsEmpty())
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{
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// Find the function.
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MakeBreakFunc = FindObject<UFunction>(/*Outer*/nullptr, *MakeBreakFunctionName, /*ExactClass*/true);
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if (!MakeBreakFunc)
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{
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NotFoundFn(MakeBreakFunctionName);
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}
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}
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}
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return MakeBreakFunc;
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}
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}
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struct FFuncs
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{
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static int Init(FPyWrapperStruct* InSelf, PyObject* InArgs, PyObject* InKwds)
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{
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const int SuperResult = PyWrapperStructType.tp_init((PyObject*)InSelf, InArgs, InKwds);
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if (SuperResult != 0)
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{
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return SuperResult;
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}
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return FPyWrapperStruct::MakeStruct(InSelf, InArgs, InKwds);
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}
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};
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GeneratedWrappedType->PyType.tp_init = (initproc)&FFuncs::Init;
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// python wrapper 给每个类型都映射了 to_tuple 函数，会调用类型的 break 函数转换为 tuple
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static PyObject* ToTuple(FPyWrapperStruct* InSelf)
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{
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return FPyWrapperStruct::BreakStruct(InSelf);
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}
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....
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{ "to_tuple", PyCFunctionCast(&FMethods::ToTuple), METH_NOARGS, "to_tuple(self) -> Tuple[object, ...] -- break this Unreal struct into a tuple of its properties" },
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```
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