转载官方文档 https://docs.unrealengine.com/4.27/zh-CN/ProgrammingAndScripting/GameplayArchitecture/Interfaces/

接口有助于确保一组(可能)不想关的类实现一组通用函数。

例如，某个游戏的系统，系统有一个触发器体积可以激活陷阱/警示敌人/向玩家奖励点数

可以对陷阱 敌人和点数奖励器 执行ReactedTrigger 函数实现，然后陷阱可能派生 AActor，敌人可能派生自专门的APawn或ACharacter 子类，点数可能派生自UDataAsset，无Uobject之外共同上级，这种情况推荐使用接口

ReactToTriggerInterface.h

#pragma once

#include "ReactToTriggerInterface.generated.h"

UINTERFACE(MinimalAPI, Blueprintable)
class UReactToTriggerInterface : public UInterface
{
    GENERATED_BODY()
};

class IReactToTriggerInterface
{    
    GENERATED_BODY()

public:
    /** 在此处添加接口函数声明 */
};

前缀为U 的类不需要任何构造或者其他函数，前缀为I的类包含所有的接口函数，且此类将被其他类继承，如想让蓝图实现当前接口，需要Blueprintable 说明符

在c++ 中实现接口 

Trap.h
#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "ReactToTriggerInterface.h"
#include "Trap.generated.h"

UCLASS(Blueprintable, Category="MyGame")
class ATrap : public AActor, public IReactToTriggerInterface
{
    GENERATED_BODY()

public:
    /** Add interface function overrides here. */
}

仅C++ 的接口函数

ReactToTrigger.h
public:
virtual bool ReactToTrigger();

ReactToTrigger.cpp

bool IReactToTriggerInterface::ReactToTrigger()
{
    return false;
}

当一个Actor类实现接口后，可以创建并实现一个针对该类的覆盖

Trap.h
public:
virtual bool ReactToTrigger() override;

Trap.cpp

bool ATrap::ReactToTrigger()
{
    return false;
}

这些c++接口未添加表示符 对蓝图不可见

蓝图可调用接口函数

创建蓝图可调用的接口函数，必须带BlueprintCallable ，必须使用BlueprintImplementableEvent 或BlueprintNativeEvent 且函数不能为虚拟的

ReactToTrigger.h
public:
/**只能在蓝图中实现的React To Trigger版本。*/
UFUNCTION(BlueprintCallable, BlueprintImplementableEvent, Category=Trigger Reaction)
bool ReactToTrigger();

ReactToTrigger.h
public:
/**可以在C++或蓝图中实现的React To Trigger版本。*/
UFUNCTION(BlueprintCallable, BlueprintNativeEvent, Category=Trigger Reaction)
bool ReactToTrigger();

注：NativeEvent 方法在实现需要加 _Implementation() 后缀

确定是否实现了接口

bool bIsImplemented = OriginalObject->GetClass()->ImplementsInterface(UReactToTriggerInterface::StaticClass()); // 如果OriginalObject实现了UReactToTriggerInterface，则bisimplemated将为true。

bIsImplemented = OriginalObject->Implements<UReactToTriggerInterface>(); // 如果OriginalObject实现了UReactToTrigger，bIsImplemented将为true。

IReactToTriggerInterface* ReactingObject = Cast<IReactToTriggerInterface>(OriginalObject); // 如果OriginalObject实现了UReactToTriggerInterface，则ReactingObject将为非空。

转到到其他虚幻类型

支持从一个接口转换到另外一个接口，在适当的情况下从一个接口转换到另外一个虚幻类型

IReactToTriggerInterface* ReactingObject = Cast<IReactToTriggerInterface>(OriginalObject); // 如果接口被实现，则ReactingObject将为非空。

ISomeOtherInterface* DifferentInterface = Cast<ISomeOtherInterface>(ReactingObject); // 如果ReactingObject为非空而且还实现了ISomeOtherInterface，则DifferentInterface将为非空。

AActor* Actor = Cast<AActor>(ReactingObject); // 如果ReactingObject为非空且OriginalObject为AActor或AActor派生的类，则Actor将为非空。

自定义接口简单实现

ReactToTriggerInterface.h
#pragma
#include "ReactToTriggerInterface.generated.h"

UINTERFACE(BlueprintType)
class UReactToTriggerInterface :public UInterface
{
    GENERATED_BODY()
};

class IReactToTriggerInterface
{
    GENERATED_BODY()

public:
    //pure c++
    virtual bool ReactToTriggerFunc_pure();

    //NativeEvent
    UFUNCTION(BlueprintCallable,BlueprintNativeEvent)
    bool ReactToTriggerNativeFunc();

    UFUNCTION(BlueprintCallable, BlueprintImplementableEvent)
    bool ReactToTriggerBlueprintImpFunc();
};

pawn.h

class ATrace_ProjectCharacter : public ACharacter, public IReactToTriggerInterface
{
    GENERATED_BODY()
    bool ReactToTriggerFunc_pure();

    UFUNCTION(BlueprintCallable,BlueprintNativeEvent)
        bool ReactToTriggerNativeFunc();

    UFUNCTION(BlueprintCallable, BlueprintImplementableEvent)
        bool ReactToTriggerBlueprintImpFunc();

};

pawn.cpp
bool ATrace_ProjectCharacter::ReactToTriggerFunc_pure()
{
    return false;
}

bool ATrace_ProjectCharacter::ReactToTriggerNativeFunc_Implementation()
{
    return false;
}