UE4中类自动生成代码解析

本文章由cartzhang编写，转载请注明出处。 所有权利保留。
文章链接：http://blog.csdn.net/cartzhang/article/details/73189272
作者：cartzhang

一、 UE4 C++ 代码自动生成流程

1. 界面点击生成C++类

图1

先调用 SMenuEntryBlock::OnClicked ，然后调用UI_COMMAND(AddCodeToProject) —-> FMainFrameActionCallbacks::AddCodeToProject()，—-> OpenAddCodeToProjectDialog来打开基类选择界面。

2. 点击Create Class按钮

图2

OnFinished(this, &SNewClassDialog::FinishClicked)

调用函数SNewClassDialog::FinishClicked()—>AddCodeToProject —>GameProjectUtils::AddCodeToProject_Internal(核心都在这里实现)

3. 头文件生成

拼接文件路径信息，GameProjectUtils::GenerateClassHeaderFile来生成头文件的内容。

FinalOutput = "// Fill out your copyright notice in the Description page of Project Settings.#pragma once#include "GameFramework/Pawn.h"#include "MyPawn.generated.h"UCLASS()class HOWTO_VTE_API AMyPawn : public APawn{    GENERATED_BODY()public:    // Sets default values for this pawn's properties    AMyPawn();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;};"

4. 生成CPP文件

GenerateClassCPPFile

CPP = // Fill out your copyright notice in the Description page of Project Settings.#include "HowTo_VTE.h"#include "MyPawn.h"// Sets default valuesAMyPawn::AMyPawn(){    // Set this pawn to call Tick() every frame.  You can turn this off to improve performance if you don't need it.    PrimaryActorTick.bCanEverTick = true;}// Called when the game starts or when spawnedvoid AMyPawn::BeginPlay(){    Super::BeginPlay();    %CURSORFOCUSLOCATION%}// Called every framevoid AMyPawn::Tick(float DeltaTime){    Super::Tick(DeltaTime);}// Called to bind functionality to inputvoid AMyPawn::SetupPlayerInputComponent(UInputComponent* PlayerInputComponent){    Super::SetupPlayerInputComponent(PlayerInputComponent);}

5. 编译

检测是否可避免全部编译工程，自动热加载，代码首次编译，RecompileModule —>
CheckForFinishedModuleDLLCompile

图3

6. 工程重新加载。

代码生成完毕。

二、 一张图

图4

一图千言

三、 文件生成模板

UE4 代码写的很精妙！

看模板头文件生成：

FString FinalOutput = Template.Replace(TEXT("%COPYRIGHT_LINE%"), *MakeCopyrightLine(), ESearchCase::CaseSensitive);    FinalOutput = FinalOutput.Replace(TEXT("%UNPREFIXED_CLASS_NAME%"), *UnPrefixedClassName, ESearchCase::CaseSensitive);    FinalOutput = FinalOutput.Replace(TEXT("%CLASS_MODULE_API_MACRO%"), *ModuleAPIMacro, ESearchCase::CaseSensitive);    FinalOutput = FinalOutput.Replace(TEXT("%UCLASS_SPECIFIER_LIST%"), *MakeCommaDelimitedList(ClassSpecifierList, false), ESearchCase::CaseSensitive);    FinalOutput = FinalOutput.Replace(TEXT("%PREFIXED_CLASS_NAME%"), *PrefixedClassName, ESearchCase::CaseSensitive);    FinalOutput = FinalOutput.Replace(TEXT("%PREFIXED_BASE_CLASS_NAME%"), *PrefixedBaseClassName, ESearchCase::CaseSensitive);    FinalOutput = FinalOutput.Replace(TEXT("%EVENTUAL_CONSTRUCTOR_DECLARATION%"), *EventualConstructorDeclaration, ESearchCase::CaseSensitive);    FinalOutput = FinalOutput.Replace(TEXT("%CLASS_PROPERTIES%"), *ClassProperties, ESearchCase::CaseSensitive);    FinalOutput = FinalOutput.Replace(TEXT("%CLASS_FUNCTION_DECLARATIONS%"), *ClassFunctionDeclarations, ESearchCase::CaseSensitive);    FinalOutput = FinalOutput.Replace(TEXT("%BASE_CLASS_INCLUDE_DIRECTIVE%"), *BaseClassIncludeDirective, ESearchCase::CaseSensitive);

CPP文件也类似的。

其中，Tmplate得到是某个继承类的模板字符串，然后通过特定符号来进行替换，生成文件。

模板文件的路径在：UE4_source\UnrealEngine\Engine\Content\Editor\Templates\

比如测试的继承基类为Pawn，他们的模板头文件和CPP文件分别为： PawnClass.h.template 和PawnClass.cpp.template 。
可以自行打开和修改文件。

PawnClass.h.template

%COPYRIGHT_LINE%#pragma once%BASE_CLASS_INCLUDE_DIRECTIVE%#include "%UNPREFIXED_CLASS_NAME%.generated.h"UCLASS(%UCLASS_SPECIFIER_LIST%)class %CLASS_MODULE_API_MACRO%%PREFIXED_CLASS_NAME% : public %PREFIXED_BASE_CLASS_NAME%{    GENERATED_BODY()public:    // Sets default values for this pawn's properties    %PREFIXED_CLASS_NAME%();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;    %CLASS_FUNCTION_DECLARATIONS%    %CLASS_PROPERTIES%};

PawnClass.cpp.template

%COPYRIGHT_LINE%#include "%MODULE_INCLUDE_PATH%"#include "%UNPREFIXED_CLASS_NAME%.h"%ADDITIONAL_INCLUDE_DIRECTIVES%// Sets default values%PREFIXED_CLASS_NAME%::%PREFIXED_CLASS_NAME%(){    // Set this pawn to call Tick() every frame.  You can turn this off to improve performance if you don't need it.    PrimaryActorTick.bCanEverTick = true;}// Called when the game starts or when spawnedvoid %PREFIXED_CLASS_NAME%::BeginPlay(){    Super::BeginPlay();    %CURSORFOCUSLOCATION%}// Called every framevoid %PREFIXED_CLASS_NAME%::Tick(float DeltaTime){    Super::Tick(DeltaTime);}// Called to bind functionality to inputvoid %PREFIXED_CLASS_NAME%::SetupPlayerInputComponent(UInputComponent* PlayerInputComponent){    Super::SetupPlayerInputComponent(PlayerInputComponent);}%ADDITIONAL_MEMBER_DEFINITIONS%

是不是可以自定义头文件呢，估计可以。暂时没有研究。

UE4 工程量太大了，什么样脑子才能架构这玩意啊，他们都是天才！

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UE4Paragon游戏人物截图！

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