17. UE5 RPG使用匿名函数替换事件委托

上一节里面，我们实现了GE被应用时的事件委托，在GE被应用到目标身上时，会触发GE身上设置的Tag，然后通过Tag在设置的表格内寻找表格数据，并添加到窗口显示。

下面，为了防止OverlayWidgetController里面的回调太臃肿，这一节我们将它的代码优化一下。

首先看一下现在的OverlayWidgetController的代码。

OverlayWidgetController.h

// 版权归暮志未晚所有。

#pragma once

#include "CoreMinimal.h"
#include "UI/WidgetController/MyWidgetController.h"
#include "OverlayWidgetController.generated.h"

class UMyUserWidget;

USTRUCT(BlueprintType)
struct FUIWidgetRow : public FTableRowBase
{
	GENERATED_BODY();

	UPROPERTY(EditAnywhere, BlueprintReadOnly)
	FGameplayTag MessageTag = FGameplayTag();

	UPROPERTY(EditAnywhere, BlueprintReadOnly)
	FText Message = FText();

	UPROPERTY(EditAnywhere, BlueprintReadOnly)
	TSubclassOf<class UMyUserWidget> MessageWidget;

	UPROPERTY(EditAnywhere, BlueprintReadOnly)
	UTexture2D* Image = nullptr;
};

DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnHealthChangedSignature, float, NewHealth);
DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnMaxHealthChangedSignature,float, NewMaxHealth);
DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnManaChangedSignature,float, NewMana);
DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnMaxManaChangedSignature,float, NewMaxMana);

DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FMessageWidgetRowSignature,FUIWidgetRow, Row);

/**
 * 屏幕覆盖用户控件控制器层基类，继承与用户控件控制器
 */
UCLASS(BlueprintType, Blueprintable)
class AURA_API UOverlayWidgetController : public UMyWidgetController
{
	GENERATED_BODY()

public:
	virtual void BroadcastInitialValues() override;
	virtual void BindCallbacksToDependencies() override;

	UPROPERTY(BlueprintAssignable, Category="GAS|Attributes")
	FOnHealthChangedSignature OnHealthChanged;

	UPROPERTY(BlueprintAssignable, Category="GAS|Attributes")
	FOnMaxHealthChangedSignature OnMaxHealthChanged;

	UPROPERTY(BlueprintAssignable, Category="GAS|Attributes")
	FOnManaChangedSignature OnManaChanged;

	UPROPERTY(BlueprintAssignable, Category="GAS|Attributes")
	FOnMaxManaChangedSignature OnMaxManaChanged;

	UPROPERTY(BlueprintAssignable, Category="GAS|Messages")
	FMessageWidgetRowSignature MessageWidgetRowDelegate;

protected:
	//EditDefaultsOnly 说明此属性可以通过属性窗口编辑，但只能在原型上进行。
	UPROPERTY(EditDefaultsOnly, BlueprintReadOnly, Category="Widget Data")
	TObjectPtr<UDataTable> MessageWidgetDataTable;
	
	void HealthChanged(const FOnAttributeChangeData& Data) const;
	void MaxHealthChanged(const FOnAttributeChangeData& Data) const;
	void ManaChanged(const FOnAttributeChangeData& Data) const;
	void MaxManaChanged(const FOnAttributeChangeData& Data) const;

	//根据传入的表格和Tag返回查找到的数据，表格类型不确定，所以使用T来表示，在使用此函数时，需要指定对应类型
	template<typename T>
	T* GetDataTableRowByTag(UDataTable* DataTable, const FGameplayTag& Tag);
};

template <typename T>
T* UOverlayWidgetController::GetDataTableRowByTag(UDataTable* DataTable, const FGameplayTag& Tag)
{
	T* Row = DataTable->FindRow<T>(Tag.GetTagName(), TEXT(""));
	return Row;
}

OverlayWidgetController.cpp

// 版权归暮志未晚所有。


#include "UI/WidgetController/OverlayWidgetController.h"

#include "AbilitySystem/AbilitySystemComponentBase.h"
#include "AbilitySystem/AttributeSetBase.h"

void UOverlayWidgetController::BroadcastInitialValues()
{
	const UAttributeSetBase* AttributeSetBase = CastChecked<UAttributeSetBase>(AttributeSet);

	OnHealthChanged.Broadcast(AttributeSetBase->GetHealth());
	OnMaxHealthChanged.Broadcast(AttributeSetBase->GetMaxHealth());
	OnManaChanged.Broadcast(AttributeSetBase->GetMana());
	OnMaxManaChanged.Broadcast(AttributeSetBase->GetMaxMana());
}

void UOverlayWidgetController::BindCallbacksToDependencies()
{
	const UAttributeSetBase* AttributeSetBase = CastChecked<UAttributeSetBase>(AttributeSet);

	AbilitySystemComponent->GetGameplayAttributeValueChangeDelegate(
		AttributeSetBase->GetHealthAttribute()).AddUObject(this, &UOverlayWidgetController::HealthChanged);

	AbilitySystemComponent->GetGameplayAttributeValueChangeDelegate(
	AttributeSetBase->GetMaxHealthAttribute()).AddUObject(this, &UOverlayWidgetController::MaxHealthChanged);

	AbilitySystemComponent->GetGameplayAttributeValueChangeDelegate(
		AttributeSetBase->GetManaAttribute()).AddUObject(this, &UOverlayWidgetController::ManaChanged);

	AbilitySystemComponent->GetGameplayAttributeValueChangeDelegate(
		AttributeSetBase->GetMaxManaAttribute()).AddUObject(this, &UOverlayWidgetController::MaxManaChanged);

	//AddLambda 绑定匿名函数
	Cast<UAbilitySystemComponentBase>(AbilitySystemComponent)->EffectAssetTags.AddLambda(
		[this](const FGameplayTagContainer& AssetTags) //中括号添加this是为了保证内部能够获取类的对象
		{
			for(const FGameplayTag& Tag : AssetTags)
			{

				//对标签进行检测，如果不是信息标签，将无法进行广播
				FGameplayTag MessageTag = FGameplayTag::RequestGameplayTag(FName("Message"));
				// "A.1".MatchesTag("A") will return True, "A".MatchesTag("A.1") will return False
				if(Tag.MatchesTag(MessageTag))
				{
					FUIWidgetRow* Row = GetDataTableRowByTag<FUIWidgetRow>(MessageWidgetDataTable, Tag);
					MessageWidgetRowDelegate.Broadcast(*Row); //前面加*取消指针引用
				}
				
				//将tag广播给Widget Controller 测试代码
				// const FString Msg = FString::Printf(TEXT("GE Tag in Widget Controller: %s"), *Tag.ToString()); //获取Asset Tag
				// GEngine->AddOnScreenDebugMessage(-1, 8.f, FColor::Cyan, Msg); //打印到屏幕上 -1 不会被覆盖

			}
		}
	);
}

void UOverlayWidgetController::HealthChanged(const FOnAttributeChangeData& Data) const
{
	OnHealthChanged.Broadcast(Data.NewValue);
}

void UOverlayWidgetController::MaxHealthChanged(const FOnAttributeChangeData& Data) const
{
	OnMaxHealthChanged.Broadcast(Data.NewValue);
}

void UOverlayWidgetController::ManaChanged(const FOnAttributeChangeData& Data) const
{
	OnManaChanged.Broadcast(Data.NewValue);
}

void UOverlayWidgetController::MaxManaChanged(const FOnAttributeChangeData& Data) const
{
	OnMaxManaChanged.Broadcast(Data.NewValue);
}

优化宏

以上为现在的代码，我们能够优化的是，将宏的设置这一块

DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnHealthChangedSignature, float, NewHealth);
DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnMaxHealthChangedSignature,float, NewMaxHealth);
DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnManaChangedSignature,float, NewMana);
DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnMaxManaChangedSignature,float, NewMaxMana);

我们可以使用一个宏作为代替，毕竟它们都是返回一个值，我们可以修改只使用一个类型

DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnAttributeChangedSignature, float, NewAttribute);

然后将委托的参数都替换成"FOnAttributeChangedSignature"即可。

	UPROPERTY(BlueprintAssignable, Category="GAS|Attributes")
	FOnAttributeChangedSignature OnHealthChanged;

	UPROPERTY(BlueprintAssignable, Category="GAS|Attributes")
	FOnAttributeChangedSignature OnMaxHealthChanged;

	UPROPERTY(BlueprintAssignable, Category="GAS|Attributes")
	FOnAttributeChangedSignature OnManaChanged;

	UPROPERTY(BlueprintAssignable, Category="GAS|Attributes")
	FOnAttributeChangedSignature OnMaxManaChanged;

使用匿名函数，代替命名函数

现在，我们每个触发委托是先通过定义了一个函数，然后将函数添加到委托里面触发，并在函数里面对属性变化的委托进行广播的。这个函数我们也可以修改成匿名了，这样可以减少很多代码量。

以下为一个委托的当前代码量：

	void HealthChanged(const FOnAttributeChangeData& Data) const;
	
	AbilitySystemComponent->GetGameplayAttributeValueChangeDelegate(
		AttributeSetBase->GetHealthAttribute()).AddUObject(this, &UOverlayWidgetController::HealthChanged);
		
void UOverlayWidgetController::HealthChanged(const FOnAttributeChangeData& Data) const
{
	OnHealthChanged.Broadcast(Data.NewValue);
}

我们可以将这些内容优化成一个匿名函数的方式，以下为优化后的方式，而且位置放到了一块

	AbilitySystemComponent->GetGameplayAttributeValueChangeDelegate(
	AttributeSetBase->GetHealthAttribute()).AddLambda(
		[this](const FOnAttributeChangeData& Data)
		{
			OnHealthChanged.Broadcast(Data.NewValue);
		}
	);

并且我们可以直接写成一行，这样，更方便查看。

优化结果

接下来我们看一下优化完成后的结果

OverlayWidgetController.h

// 版权归暮志未晚所有。

#pragma once

#include "CoreMinimal.h"
#include "UI/WidgetController/MyWidgetController.h"
#include "OverlayWidgetController.generated.h"

class UMyUserWidget;

USTRUCT(BlueprintType)
struct FUIWidgetRow : public FTableRowBase
{
	GENERATED_BODY();

	UPROPERTY(EditAnywhere, BlueprintReadOnly)
	FGameplayTag MessageTag = FGameplayTag();

	UPROPERTY(EditAnywhere, BlueprintReadOnly)
	FText Message = FText();

	UPROPERTY(EditAnywhere, BlueprintReadOnly)
	TSubclassOf<class UMyUserWidget> MessageWidget;

	UPROPERTY(EditAnywhere, BlueprintReadOnly)
	UTexture2D* Image = nullptr;
};

DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnAttributeChangedSignature, float, NewAttribute);

DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FMessageWidgetRowSignature,FUIWidgetRow, Row);

/**
 * 屏幕覆盖用户控件控制器层基类，继承与用户控件控制器
 */
UCLASS(BlueprintType, Blueprintable)
class AURA_API UOverlayWidgetController : public UMyWidgetController
{
	GENERATED_BODY()

public:
	virtual void BroadcastInitialValues() override;
	virtual void BindCallbacksToDependencies() override;

	UPROPERTY(BlueprintAssignable, Category="GAS|Attributes")
	FOnAttributeChangedSignature OnHealthChanged;

	UPROPERTY(BlueprintAssignable, Category="GAS|Attributes")
	FOnAttributeChangedSignature OnMaxHealthChanged;

	UPROPERTY(BlueprintAssignable, Category="GAS|Attributes")
	FOnAttributeChangedSignature OnManaChanged;

	UPROPERTY(BlueprintAssignable, Category="GAS|Attributes")
	FOnAttributeChangedSignature OnMaxManaChanged;

	UPROPERTY(BlueprintAssignable, Category="GAS|Messages")
	FMessageWidgetRowSignature MessageWidgetRowDelegate;

protected:
	//EditDefaultsOnly 说明此属性可以通过属性窗口编辑，但只能在原型上进行。
	UPROPERTY(EditDefaultsOnly, BlueprintReadOnly, Category="Widget Data")
	TObjectPtr<UDataTable> MessageWidgetDataTable;

	//根据传入的表格和Tag返回查找到的数据，表格类型不确定，所以使用T来表示，在使用此函数时，需要指定对应类型
	template<typename T>
	T* GetDataTableRowByTag(UDataTable* DataTable, const FGameplayTag& Tag);
};

template <typename T>
T* UOverlayWidgetController::GetDataTableRowByTag(UDataTable* DataTable, const FGameplayTag& Tag)
{
	T* Row = DataTable->FindRow<T>(Tag.GetTagName(), TEXT(""));
	return Row;
}

OverlayWidgetController.cpp

// 版权归暮志未晚所有。


#include "UI/WidgetController/OverlayWidgetController.h"

#include "AbilitySystem/AbilitySystemComponentBase.h"
#include "AbilitySystem/AttributeSetBase.h"

void UOverlayWidgetController::BroadcastInitialValues()
{
	const UAttributeSetBase* AttributeSetBase = CastChecked<UAttributeSetBase>(AttributeSet);

	OnHealthChanged.Broadcast(AttributeSetBase->GetHealth());
	OnMaxHealthChanged.Broadcast(AttributeSetBase->GetMaxHealth());
	OnManaChanged.Broadcast(AttributeSetBase->GetMana());
	OnMaxManaChanged.Broadcast(AttributeSetBase->GetMaxMana());
}

void UOverlayWidgetController::BindCallbacksToDependencies()
{
	const UAttributeSetBase* AttributeSetBase = CastChecked<UAttributeSetBase>(AttributeSet);

	AbilitySystemComponent->GetGameplayAttributeValueChangeDelegate(AttributeSetBase->GetHealthAttribute()).AddLambda([this](const FOnAttributeChangeData& Data){OnHealthChanged.Broadcast(Data.NewValue);});
	AbilitySystemComponent->GetGameplayAttributeValueChangeDelegate(AttributeSetBase->GetMaxHealthAttribute()).AddLambda([this](const FOnAttributeChangeData& Data){OnMaxHealthChanged.Broadcast(Data.NewValue);});
	AbilitySystemComponent->GetGameplayAttributeValueChangeDelegate(AttributeSetBase->GetManaAttribute()).AddLambda([this](const FOnAttributeChangeData& Data){OnManaChanged.Broadcast(Data.NewValue);});
	AbilitySystemComponent->GetGameplayAttributeValueChangeDelegate(AttributeSetBase->GetMaxManaAttribute()).AddLambda([this](const FOnAttributeChangeData& Data){OnMaxManaChanged.Broadcast(Data.NewValue);});

	//AddLambda 绑定匿名函数
	Cast<UAbilitySystemComponentBase>(AbilitySystemComponent)->EffectAssetTags.AddLambda(
		[this](const FGameplayTagContainer& AssetTags) //中括号添加this是为了保证内部能够获取类的对象
		{
			for(const FGameplayTag& Tag : AssetTags)
			{

				//对标签进行检测，如果不是信息标签，将无法进行广播
				FGameplayTag MessageTag = FGameplayTag::RequestGameplayTag(FName("Message"));
				// "A.1".MatchesTag("A") will return True, "A".MatchesTag("A.1") will return False
				if(Tag.MatchesTag(MessageTag))
				{
					FUIWidgetRow* Row = GetDataTableRowByTag<FUIWidgetRow>(MessageWidgetDataTable, Tag);
					MessageWidgetRowDelegate.Broadcast(*Row); //前面加*取消指针引用
				}
				
				//将tag广播给Widget Controller 测试代码
				// const FString Msg = FString::Printf(TEXT("GE Tag in Widget Controller: %s"), *Tag.ToString()); //获取Asset Tag
				// GEngine->AddOnScreenDebugMessage(-1, 8.f, FColor::Cyan, Msg); //打印到屏幕上 -1 不会被覆盖

			}
		}
	);
}

优化最大的还是cpp文件，清晰了不少，而且代码还更加的精简。

运行调试

我们在运行起来UE，会提示有两个蓝图文件出现问题，它们的问题相同都是因为修改代码后，委托的类型变化造成的。

进入后编译会提示错误，我们找到错误的地方查看

右键点击刷新节点

刷新以后，重新链接新的属性即可。