A、普通的C++类型 F Class
B、智能指针
C、UObject类型的UClass
我们逐一说明他们的使用方法和注意事项
1、针对普通的C++的class照普通的使用方式即可;UED中或者UE4的底层很多使用这种Class的例子;但UE4会统一的在前加F 比如:上次我们说的负责座标轴绘制和处理的FWidget类(在UnrealWidget.h中)
声明:
class FWidget
: public FGCObject
{
FWidget();
};
使用:
FEditorViewportClient::FEditorViewportClient(FEditorModeTools* InModeTools, FPreviewScene* InPreviewScene, const TWeakPtr<SEditorViewport>& InEditorViewportWidget)
: bAllowCinematicPreview(false)
...
, Widget(new FWidget)
销毁:
FEditorViewportClient::~FEditorViewportClient()
{
...
delete Widget;
}
目前大部分的F Class都在UED的框架中使用。在game的框架中相同功能的Class都改成了UClass
2、UE4的智能指针SmartPointer体系在引擎初期项目中用处主要在UI上;SlateUI是主要使用智能指针的地方。但随着后期UMG的出现SlateUI的部分被完全封装在UMG内部,现在研发人员一般不会接触到这一块。但对于研究引擎的人来说熟悉智能指针相当重要。以SWidget为例说明
声明方式():
class SLATECORE_API SWidget
: public FSlateControlledConstruction,
public TSharedFromThis<SWidget> // Enables 'this->AsShared()'
{
friend struct FCurveSequence;
//dubeibei XMod
friend class UXScriptWidget;
public:
};
重点是类模版TSharedFromThis<SWidget>;TSharedPtr<>;TSharedRef<>
template< class ObjectType, ESPMode Mode >
class TSharedFromThis
{};
template< class ObjectType, ESPMode Mode >
class TSharedPtr
{};
template< class ObjectType, ESPMode Mode >
class TSharedRef
{};
template< class ObjectType, ESPMode Mode >
class TWeakPtr
{
public:
};
详情见:SharedPointer.h 其中指针会有SharedReferenceCount保存计数;计数为0时自动清理。TWeakPtr中有WeakReferenceCount保存计数,但TWeakPtr的引用计数不作为是否清理的标记,即TweakPtr中的Object可能已经被清理;但TweakPtr还在;可使用TWeakPtr的Isvalid来校验Object是否已被清理。
使用方式:
TSharedPtr<SWidget> RetWidget = SNew(SInvalidationPanel)
或者:
SAssignNew(MyTextBlock, STextBlock)
或者:
MakeShareable(new FUIController()); 返回的也是一个TSharedPtr
关于TSharedPtr TSharedRef TWeakPtr之间相互转换的使用:
TSharedPtr ToSharedRef()-> TSharedRef
TWeakPtr Pin()-> TSharedPtr
TSharedRef
转换使用StaticCastSharedPtr:
TSharedPtr<SChannelListPageWidget> MyWidget = StaticCastSharedPtr<SChannelListPageWidget>(GetWidget());
3、关于 UObject的Class使用
UObject是上层或者Game框架里面最经常用到的Class。把游戏框架中出现的各种东西抽象出一个UObject十分必要;通用的属性和接口;统一的GC;方便数据统计;等等
声明示例如下:
UCLASS(config = Game, meta = (ChildCanTick))
class PROJECTZ_API AMaterialParamaterObject : public AActor
{
GENERATED_UCLASS_BODY()
/** The CapsuleComponent being used for movement collision (by CharacterMovement). Always treated as being vertically aligned in simple collision check functions. */
UPROPERTY(Category = Character, VisibleAnywhere, BlueprintReadOnly)
class USceneComponent* RootSceneCom;
/** The main skeletal mesh associated with this Character (optional sub-object). */
UPROPERTY(Category = MapEditor, VisibleAnywhere, BlueprintReadOnly)
class UStaticMeshComponent* Mesh;
static FName MeshComponentName;
static FName RootComponentName;
UFUNCTION(BlueprintCallable, Category = "MapEditor|Objects")
void ChangeFloatParamater(int32 ParaIndex, int32 NameIndex, float InValue);
UFUNCTION(BlueprintCallable, Category = "MapEditor|Objects")
void ChangeIntParamater(int32 ParaIndex, int32 NameIndex, int32 InValue);
UFUNCTION(BlueprintCallable, Category = "MapEditor|Objects")
void ChangeVectorParamater(int32 ParaIndex, int32 NameIndex, FVector InValue);
UFUNCTION(BlueprintCallable, Category = "MapEditor|Objects")
void ChangeTextureParamater(int32 ParaIndex, int32 NameIndex, UTexture2D* InValue);
UPROPERTY(Category = "MapEditor|Objects", EditAnywhere, BlueprintReadWrite)
TArray<FEditorMaterialParamater> Paramaters;
};
关于UHT:UnrealHeaderTool,UHT会根据UClass的头文件.h生成.generated.h文件把其中拥有UPROPERTY UFUNCTION的标签的重新定义例如ChangeFloatParamater接口:
DECLARE_FUNCTION(execChangeFloatParamater) \
{ \
P_GET_PROPERTY(UIntProperty,Z_Param_ParaIndex); \
P_GET_PROPERTY(UIntProperty,Z_Param_NameIndex); \
P_GET_PROPERTY(UFloatProperty,Z_Param_InValue); \
P_FINISH; \
P_NATIVE_BEGIN; \
this->ChangeFloatParamater(Z_Param_ParaIndex,Z_Param_NameIndex,Z_Param_InValue); \
P_NATIVE_END; \
}
新生成的.genreated.h文件会加入编译所有的UPROPERTY和UFUNCTION都会是继承自UObject的Class使用 ;然后再由GC统一的管理UObject;
不加UPROPETY标签的属性不在UObject 此过程GC的范围之内;需要另外的控制,不然很容易内存泄漏。见下章详细说明。
使用:
MyGCProtectedObj = NewObject<UMyObjectClass>(this);
如果不想让UObject强制回收可设置:
YourObjectInstance->AddToRoot();
销毁:
if(!MyObject) return;
if(!MyObject->IsValidLowLevel()) return;
MyObject->ConditionalBeginDestroy(); //instantly clears UObject out of memory
MyObject = nullptr;
销毁Actor:
if(!TheCharacter) return;
if(!TheCharacter->IsValidLowLevel()) return;
TheCharacter->Destroy();
TheCharacter->ConditionalBeginDestroy(); //essential extra step, in all my testing