45 lines
1.7 KiB
Markdown
45 lines
1.7 KiB
Markdown
|
# ref
|
|||
|
|
|
|||
|
|
- **功能描述：** 使得函数的参数变成引用类型
|
|||
|
|
|
|||
|
|
- **元数据类型：** bool
|
|||
|
|
- **引擎模块：** Blueprint, Parameter
|
|||
|
|
- **作用机制：** 在PropertyFlags中加入[CPF_ReferenceParm](../../../../Flags/EPropertyFlags/CPF_ReferenceParm.md)
|
|||
|
|
- **常用程度：★★★★★**
|
|||
|
|
|
|||
|
|
普通参数和引用参数的区别是，在获取参数的时候，Ref类型会直接获得实参的引用，而不是拷贝。这样就可以避免拷贝，保存修改。
|
|||
|
|
|
|||
|
|
单纯的&参数是会被解析成输出返回参数，因此要用ref再继续标明。
|
|||
|
|
|
|||
|
|
## 测试代码：
|
|||
|
|
|
|||
|
|
```cpp
|
|||
|
|
//PropertyFlags: CPF_Parm | CPF_OutParm | CPF_ZeroConstructor | CPF_IsPlainOldData | CPF_NoDestructor | CPF_HasGetValueTypeHash | CPF_NativeAccessSpecifierPublic
|
|||
|
|
UFUNCTION(BlueprintCallable)
|
|||
|
|
FString MyFuncTestParam_Default(int& refValue);
|
|||
|
|
|
|||
|
|
//PropertyFlags: CPF_Parm | CPF_OutParm | CPF_ZeroConstructor | CPF_ReferenceParm | CPF_IsPlainOldData | CPF_NoDestructor | CPF_HasGetValueTypeHash | CPF_NativeAccessSpecifierPublic
|
|||
|
|
UFUNCTION(BlueprintCallable)
|
|||
|
|
FString MyFuncTestParam_Ref(UPARAM(ref) int& refValue);
|
|||
|
|
|
|||
|
|
UFUNCTION(BlueprintCallable)
|
|||
|
|
FString MyFuncTestParam_Copy(int value);
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
## 蓝图的代码：
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
## 原理：
|
|||
|
|
|
|||
|
|
ref参数在UHT生成时会用P_GET_PROPERTY_REF来获得
|
|||
|
|
|
|||
|
|
```cpp
|
|||
|
|
#define P_GET_PROPERTY(PropertyType, ParamName) \
|
|||
|
|
PropertyType::TCppType ParamName = PropertyType::GetDefaultPropertyValue(); \
|
|||
|
|
Stack.StepCompiledIn<PropertyType>(&ParamName);
|
|||
|
|
|
|||
|
|
#define P_GET_PROPERTY_REF(PropertyType, ParamName) \
|
|||
|
|
PropertyType::TCppType ParamName##Temp = PropertyType::GetDefaultPropertyValue(); \
|
|||
|
|
PropertyType::TCppType& ParamName = Stack.StepCompiledInRef<PropertyType, PropertyType::TCppType>(&ParamName##Temp);
|
|||
|
|
```
|