工厂方法模式

复制代码

#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

复制代码

#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

复制代码

#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;
}