01. 简单工厂模式

前言：设计模式方面，很多是多态模式的实现。多态涉及继承和指针。

简单工程模式：有一个工程类，可以根据输入进行生产不同的对象指针。其代码和运行结果如下：

/**
 * @file car_factory.h
 * @brief car factory
 * @author timeshark
 * @version 1.0
 * @date 2018-08-06
 */

#ifndef CAR_FACTORY
#define CAR_FACTORY

#include <iostream>
#include <string>

using std::cout;
using std::endl;
using std::string;

class Car {
public:
    virtual void print() = 0;
};

class Benz : public Car {
public:
    void print() {
        cout << "this is benz" << endl;
    }
};

class Bmw : public Car {
public:
    void print() {
        cout << "this is bmw" << endl;
    }
};

class Factory {
public:
    Car* create_car(string name) {
        if (0 == name.compare("benz")) {
            cout << "create benz" << endl;
            return new Benz();
        } else if (0 == name.compare("bmw")) {
            cout << "create bmw" << endl;
            return new Bmw();
        } else {
            cout << "no this car" << endl;
            return NULL;
        }
    }
};

#endif

/**
 * @file main.cpp
 * @brief simple factory
 * @author timeshark
 * @version 1.0
 * @date 2018-08-06
 */

#include "car_factory.h"

int main() {
    Factory myfactory;

    Car* b = myfactory.create_car("benz");
    if (b) {
        b->print();
    }

    Car* c = myfactory.create_car("bmw");
    if (c) {
        c->print();
    }

    Car* d = myfactory.create_car("empty");
    if (d) {
        d->print();
    }

    return 0;
}

输出：