UE5 C++（十四）— Interface的使用

本文介绍: 接口是一系列抽象方法的声明，是一些方法特征的集合，这些方法都应该是抽象的，需要由具体的类去实现，然后第三方就可以通过这组抽象方法调用，让具体的类执行具体的方法。接口类中不可以声明成员变量，静态变量。可以声明静态常量作为接口的返回值状态，需要在对应的cpp中定义并初始化，访问时需要使用”接口类型::静态常量名”访问定义的接口方法使用virtual 修饰符和 “=0” 修饰，表示该方法是纯虚的。因为接口类是无法创建对象的，所以不应该编写构造函数和析构函数。

接口是一系列抽象方法的声明，是一些方法特征的集合，这些方法都应该是抽象的，需要由具体的类去实现，然后第三方就可以通过这组抽象方法调用，让具体的类执行具体的方法。

用c++实现接口类时需要注意一下几点：

主要实现小鸟：==> 出生 ==> 飞行 ==> 活动区域 ==> 死亡这个过程

实现-接口类-飞行动作
IAction.h

#ifndef IACTION_H
#define IACTION_H
//接口类 表示飞行动作
class IAction
{
public:
    virtual void fly() = 0;
};

#endif // IACTION_H

实现-接口类-活动区域
IShape.h

#ifndef ISHAPE_H
#define ISHAPE_H

// 接口类 表示活动区域
class IShape
{
public:
    virtual int area() = 0;
    static const int MIN_AREA;
};

#endif // ISHAPE_H

#include "IShape.h"
 
const int IShape::MIN_AREA = 0;

// 这是一种防止多次包含头文件的预处理器技术
#ifndef BIRD_H
#define BIRD_H

#include "IAction.h"
#include "IShape.h"

class Bird : public IShape, public IAction
{
public:
    Bird();
    ~Bird();

    // IAction interface
public:
    void fly() override;

    // IShape interface
public:
    int area() override;
};

#endif // BIRD_H

#include "Bird.h"
#include <iostream>

Bird::Bird()
{
    std::cout << "initialize : The bird is born. " << std::endl;
}

Bird::~Bird()
{
    std::cout << "dispose : The bird is die." << std::endl;
}

void Bird::fly()
{
    std::cout << "execute : The bird is flying. " << std::endl;
}

int Bird::area()
{
    std::cout << "activity area : " << IShape::MIN_AREA << std::endl;
    return 0;
}

#include "Bird.h"

int main()
{
    Bird *bird = new Bird();
    bird->fly();
    bird->area();
    delete bird;
    return 0;
}

PS D:ProjectC++TempCppinterface> g++ main.cpp Bird.cpp IShape.cpp -o main.exe

PS D:ProjectC++TempCppinterface> ./main.exe

initialize : The bird is born. 
execute : The bird is flying.
activity area : 0
dispose : The bird is die.

	virtual void Attack(){};
	virtual void CaclulateHealth(){};

#pragma once

#include "CoreMinimal.h"
#include "UObject/Interface.h"
#include "MyInterface.generated.h"

// This class does not need to be modified.
UINTERFACE(MinimalAPI)
class UMyInterface : public UInterface
{
	GENERATED_BODY()
};

/**
 *
 */
class DEMO_API IMyInterface
{
	GENERATED_BODY()

	// Add interface functions to this class. This is the class that will be inherited to implement this interface.
public:
	virtual void Attack(){};
	virtual void CaclulateHealth(){};
};

#include "MyInterface.h"
#include "GameFramework/Character.h"
#include "MyCharacter.generated.h"

UCLASS()
class DEMO_API AMyCharacter : public ACharacter, public IMyInterface
{
	GENERATED_BODY()

public:
	// Sets default values for this character's properties
	AMyCharacter();

protected:
	// Called when the game starts or when spawned
	virtual void BeginPlay() override;

public:
	// Called every frame
	virtual void Tick(float DeltaTime) override;

	// Called to bind functionality to input
	virtual void SetupPlayerInputComponent(class UInputComponent *PlayerInputComponent) override;
	
	// 重写接口函数
	virtual void Attack() override;
	virtual void CaclulateHealth() override;
};

// Called when the game starts or when spawned
void AMyCharacter::BeginPlay()
{
	Super::BeginPlay();
	// 执行接口
	Attack();
	CaclulateHealth();
}
// 重写接口函数
void AMyCharacter::Attack()
{
	UE_LOG(LogTemp, Warning, TEXT("Attack"));
	GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Red, TEXT("Attack"));
}
void AMyCharacter::CaclulateHealth()
{
	UE_LOG(LogTemp, Warning, TEXT("CaclulateHealth"));
	GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Red, TEXT("CaclulateHealth"));
}