工厂方法模式

factory.h

#ifndef FACTORY_H #define FACTORY_H #include <QString> //工厂 class Factory { public: Factory(){}; // FruitFactory* p = new AppleFactory(); // // ... // delete p; // 注意：是通过基类指针删子类对象 // 如果 FruitFactory 的析构函数不是 virtual： // delete p; 只会调用 FruitFactory 的析构函数 // 不会调用 AppleFactory 的析构函数 // 结果是：AppleFactory 里自己管理的资源（比如 new 出来的内存、打开的文件、锁等）不会被释放，行为是未定义的（UB），最常见就是泄漏。 virtual ~Factory()=default; // 类型方法：返回自己的工厂类型 virtual QString getType() const = 0; }; //苹果 class AppleFactory:public Factory { public: AppleFactory(){}; QString getType()const override{ return "apple"; } }; //香蕉 class BananaFactory:public Factory { public: BananaFactory(){}; QString getType()const override{ return "banana"; } }; //葡萄 class GrapeFactory:public Factory { public: GrapeFactory(){}; QString getType()const override{ return "grape"; } }; #endif // FACTORY_H

mainwindow.h

#ifndef MAINWINDOW_H #define MAINWINDOW_H #include <QMainWindow> #include <QDebug> #include "factory.h" QT_BEGIN_NAMESPACE namespace Ui { class MainWindow; } QT_END_NAMESPACE class MainWindow : public QMainWindow { Q_OBJECT public: MainWindow(QWidget *parent = nullptr); ~MainWindow(); private: Ui::MainWindow *ui; }; #endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h" #include "ui_mainwindow.h" #include <QVector> MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent) , ui(new Ui::MainWindow) { ui->setupUi(this); AppleFactory *apple=new AppleFactory(); BananaFactory *banana=new BananaFactory(); GrapeFactory *grape=new GrapeFactory(); Factory *f1=apple; Factory *f2=banana; Factory *f3=grape; QVector<Factory*> vec; vec.push_back(f1); vec.push_back(f2); vec.push_back(f3); for (auto item:vec) { qDebug()<<item->getType(); } delete apple; delete banana; delete grape; } MainWindow::~MainWindow() { delete ui; }

运行截图：