【UE4 设计模式】工厂方法模式 Factory Method Pattern 及自定义创建资源

概述

描述

又称为工厂模式，也叫虚拟构造器(Virtual Constructor)模式，或者多态工厂(Polymorphic Factory)模式
工厂父类负责定义创建产品对象的公共接口，而工厂子类则负责生成具体的产品对象，这样做的目的是将产品类的实例化操作延迟到工厂子类中完成，即通过工厂子类来确定究竟应该实例化哪一个具体产品类。

套路

创建抽象产品类 ；
创建具体产品类，继承抽象产品类；
创建抽象工厂类
创建工厂类，继承抽象工厂类，定义具体产品类的创建方法；
通过调用具体工厂类的方法，从而创建不同具体产品类的实例

使用场景

当一个类不知道它所需要的对象的类时。使用者无需知道具体产品类的类名，只需要知道所对应的工厂即可；
当一个类希望通过其子类来指定创建对象时。由子类来创建具体产品

优缺点

优点
- 将创建实例的工作与使用实例的工作分开，实现了解耦；
- 用户只需要关心所需产品对应的工厂，无须关心创建细节，甚至无须知道具体产品类的类名。
- 加入新产品时，无须修改抽象工厂和抽象产品提供的接口，只要添加一个具体工厂和具体产品就可以了。这样更符合“开闭原则”。
缺点
- 在添加新产品时，需要编写新的具体产品类和工厂类，在一定程度上增加了系统的复杂度，
- 引入抽象层，增加了系统的抽象性和理解难度
- 一个具体工厂只能创建一种具体产品

UE4 中的工厂方法实践

自定义工厂模式实践

创建产品抽象类和产品具体类

// 产品抽象类
UCLASS(Abstract)
class DESIGNPATTERNS_API UProductObject : public UObject
{
	GENERATED_BODY()
public:
	virtual void ShowInfo() { check(0 && "You must override this");  }
};

// 产品具体类A
UCLASS()
class DESIGNPATTERNS_API UProductA : public UProductObject
{
	GENERATED_BODY()
public:
	virtual void ShowInfo() override {
		UE_LOG(LogTemp, Warning, TEXT(__FUNCTION__" This is a ProductA"));
	}
};

// 产品具体类B
UCLASS()
class DESIGNPATTERNS_API UProductB : public UProductObject
{
	GENERATED_BODY()
public:
	virtual void ShowInfo() override {
		UE_LOG(LogTemp, Warning, TEXT(__FUNCTION__" This is a ProductB"));
	}
};

创建工厂抽象类和工厂具体类

// 工厂抽象类
UCLASS(Abstract)
class DESIGNPATTERNS_API UFactoryObject : public UObject
{
	GENERATED_BODY()
public:

	virtual UProductObject* CreateNewProduct() {
		check(0 && "You must override this");
		return nullptr;
	}
	
};

// 工厂具体类A
UCLASS(Blueprintable,BlueprintType)
class DESIGNPATTERNS_API UFactoryA : public UFactoryObject
{
	GENERATED_BODY()
public:

	virtual UProductObject* CreateNewProduct() override {
		return NewObject<UProductA>();
	}
};

// 工厂具体类B
UCLASS(Blueprintable, BlueprintType)
class DESIGNPATTERNS_API UFactoryB : public UFactoryObject
{
	GENERATED_BODY()
public:

	virtual UProductObject* CreateNewProduct() override {
		return NewObject<UProductB>();
	}
};

调用

// 调用测试用的Actor
UCLASS()
class DESIGNPATTERNS_API AFactoryActor : public AActor
{
	GENERATED_BODY()
public:
	UPROPERTY()
		UFactoryA* FactoryA;

	UPROPERTY()
		UFactoryB* FactoryB;

	void BeginPlay() override {
		// A 工厂生成 A 产品
		FactoryA = NewObject<UFactoryA>();
		UProductObject* ProductA = FactoryA->CreateNewProduct();
		ProductA->ShowInfo();

		// B 工厂生成 B 产品
		FactoryB = NewObject<UFactoryB>();
		UProductObject* ProductB = FactoryB->CreateNewProduct();
		ProductB->ShowInfo();
	}
};

调式输出

LogTemp: Warning: UProductA::ShowInfo This is a ProductA
LogTemp: Warning: UProductB::ShowInfo This is a ProductB

引擎自带工厂方法模式——自定义资源创建

继承 UObject 自定义资产类

UCLASS(Blueprintable, BlueprintType)
class DESIGNPATTERNS_API UCustomAsset : public UObject
{
	GENERATED_BODY()
public:
	UPROPERTY(EditAnywhere)
		FString ProductName;
};

继承 UFactory 的工厂类

SupportedClass 指定资产类
FactoryCreatNew 重载资产类实例化

UCLASS()
class DESIGNPATTERNS_API UUEDefaultFactory : public UFactory
{
	GENERATED_UCLASS_BODY()
public:
	
	virtual UObject* FactoryCreateNew(UClass* InClass, UObject* InParent, FName InName, EObjectFlags Flags, UObject* Context, FFeedbackContext* Warn) override;
	//virtual uint32 GetMenuCategories() const override; //4.25以前
};

UUEDefaultFactory::UUEDefaultFactory(const class FObjectInitializer& ObjectInitializer)
	: Super(ObjectInitializer)
{
	bCreateNew = true;
	bEditAfterNew = true;
	SupportedClass = UCustomAsset::StaticClass();
}

UObject* UUEDefaultFactory::FactoryCreateNew(UClass* InClass, UObject* InParent, FName InName, EObjectFlags Flags, UObject* Context, FFeedbackContext* Warn)
{
	auto newProduct = NewObject<UCustomAsset>(InParent, InClass, InName, Flags);
	return newProduct;
}

//uint32 UUEDefaultFactory::GetMenuCategories() const
//{
	//return EAssetTypeCategories::Misc;
//}

自定义模块，并添加到工程中

项目目录

DesignPatterns
	└─ Source
	       ├─ DesignPatterns
	       │    ├─ DesignPatterns.Build.cs
	       │    ├─ DesignPatterns.cpp
	       │    ├─ DesignPatterns.h
	       │    ├─ DesignPatternsGameModeBase.cpp
	       │    ├─ DesignPatternsGameModeBase.h
	       │    └─ Patterns_Factory
	       │         ├─ FactoryObject.cpp
	       │         ├─ FactoryObject.h
	       │         ├─ ProductObject.cpp
	       │         ├─ ProductObject.h
	       │         ├─ UEDefaultFactory.cpp
	       │         └─ UEDefaultFactory.h   
	       ├─ DesignPatternsEditor
	       │    ├─ DesignPatternsEditor.Build.cs
	       │    ├─ DesignPatternsEditor.cpp
	       │    └─ DesignPatternsEditor.h
	       ├─ DesignPatterns.Target.cs
	       └─ DesignPatternsEditor.Target.cs

添加 DesignPatternsEditor 模块

在Source目录下，分别添加 DesignPatternsEditor.Build.cs 、DesignPatternsEditor.cpp 、DesignPatternsEditor.h 三个文件

DesignPatternsEditor.Build.cs

using UnrealBuildTool;

public class DesignPatternsEditor : ModuleRules
{
	public DesignPatternsEditor(ReadOnlyTargetRules Target) : base(Target)
	{
		PCHUsage = PCHUsageMode.UseExplicitOrSharedPCHs;
	
		PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore", "UnrealEd", "DesignPatterns"});

		PrivateDependencyModuleNames.AddRange(new string[] {  });

		// Uncomment if you are using Slate UI
		PrivateDependencyModuleNames.AddRange(new string[] { "Slate", "SlateCore" });
		
		// Uncomment if you are using online features
		// PrivateDependencyModuleNames.Add("OnlineSubsystem");

		// To include OnlineSubsystemSteam, add it to the plugins section in your uproject file with the Enabled attribute set to true
	}
}

DesignPatternsEditor.h

4.25开始需要自定义 AssetTypeActions（继承自 FAssetTypeActions_Base），才可以在编辑器中找到

#pragma once

#include "CoreMinimal.h"
#include "AssetTypeActions_Base.h"
#include "DesignPatterns/Patterns_Factory/FactoryObject.h"

class FDesignPatternsEditorModule : public IModuleInterface
{
public:

	/** IModuleInterface implementation */
	virtual void StartupModule() override;
	virtual void ShutdownModule() override;
};

class FAssetTypeActions_CustomAsset : public FAssetTypeActions_Base
{

public:
	FAssetTypeActions_CustomAsset(){}
	FAssetTypeActions_CustomAsset(EAssetTypeCategories::Type InAssetCategory);

	virtual FColor GetTypeColor() const override { return FColor(97, 85, 212); }
	virtual void OpenAssetEditor(const TArray<UObject*>& InObjects, TSharedPtr<class IToolkitHost> EditWithinLevelEditor = TSharedPtr<IToolkitHost>()) override;

	// IAssetTypeActions Implementation
	virtual FText GetName() const override { return FText::FromName(TEXT("Custom Asset")); }
	virtual UClass* GetSupportedClass() const override { return UCustomAsset::StaticClass(); }
	virtual uint32 GetCategories() override { return MyAssetCategory; }

private:
	EAssetTypeCategories::Type MyAssetCategory;

};

DesignPatternsEditor.cpp

// Copyright Epic Games, Inc. All Rights Reserved.

#include "DesignPatternsEditor.h"
#include "Modules/ModuleManager.h"
#include "IAssetTools.h"
#include "AssetToolsModule.h"

#define LOCTEXT_NAMESPACE "FDesignPatternsEditorModule"

void FDesignPatternsEditorModule::StartupModule()
{
	IAssetTools& AssetTools = FModuleManager::LoadModuleChecked<FAssetToolsModule>("AssetTools").Get();
	//定义资产的分类名
	EAssetTypeCategories::Type AssetCategory = AssetTools.RegisterAdvancedAssetCategory(FName(TEXT("CustomKey")), FText::FromName(TEXT("CustomCategory")));
	TSharedPtr<FAssetTypeActions_CustomAsset> actionType = MakeShareable(new FAssetTypeActions_CustomAsset(AssetCategory));
	AssetTools.RegisterAssetTypeActions(actionType.ToSharedRef());
}

void FDesignPatternsEditorModule::ShutdownModule()
{
	if (FModuleManager::Get().IsModuleLoaded("AssetTools"))
	{
		IAssetTools& AssetTools = FModuleManager::Get().GetModuleChecked<FAssetToolsModule>("AssetTools").Get();
		AssetTools.UnregisterAssetTypeActions(MakeShareable(new FAssetTypeActions_CustomAsset));
	}
}

FAssetTypeActions_CustomAsset::FAssetTypeActions_CustomAsset(EAssetTypeCategories::Type InAssetCategory)
{
	MyAssetCategory = InAssetCategory;
}

void FAssetTypeActions_CustomAsset::OpenAssetEditor(const TArray<UObject*>& InObjects, TSharedPtr<class IToolkitHost> EditWithinLevelEditor /*= TSharedPtr<IToolkitHost>()*/)
{
	FSimpleAssetEditor::CreateEditor(EToolkitMode::Standalone, EditWithinLevelEditor, InObjects);
}

#undef LOCTEXT_NAMESPACE
IMPLEMENT_MODULE(FDesignPatternsEditorModule, DesignPatternsEditor);

将模块加入到 项目名.uproject 中

{
	"EngineAssociation": "4.26",
	"Modules": [
		...,
		{
			"Name": "DesignPatternsEditor",
			"Type": "Editor",
			"LoadingPhase": "Default",
			"AdditionalDependencies": [
				"Engine",
				"CoreUObject",
				"Slate",
				"SlateCore",
				"UnrealEd"
			]
		}
	]
}

将模块加入到 项目名.Target.cs 中

using UnrealBuildTool;
using System.Collections.Generic;

public class DesignPatternsEditorTarget : TargetRules
{
	public DesignPatternsEditorTarget( TargetInfo Target) : base(Target)
	{
		Type = TargetType.Editor;
		DefaultBuildSettings = BuildSettingsVersion.V2;
		ExtraModuleNames.AddRange( new string[] { "DesignPatterns", "DesignPatternsEditor" } );
	}
}

测试结果

参考

posted @ 2021-06-03 23:33 砥才人阅读(801) 评论(0) 编辑收藏举报

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【UE4 设计模式】工厂方法模式 Factory Method Pattern 及自定义创建资源

概述

描述

套路

使用场景

优缺点

UE4 中的工厂方法实践

引擎自带工厂方法模式——自定义资源创建

参考

公告