生成器模式

#include <iostream>
#include <memory>

class Product {
public:
    void setPartA(int partA) { this->partA = partA; }
    void setPartB(int partB) { this->partB = partB; }
    void setPartC(int partC) { this->partC = partC; }
    void show() {
        std::cout << "In Product. partA is " << partA << ". partB is " << partB << ". partC is " << partC << "." << std::endl;
    }
private:
    int partA = 0;
    int partB = 0;
    int partC = 0;
};

class Builder {
public:
    virtual void buildPartA() = 0;
    virtual void buildPartB() = 0;
    virtual void buildPartC() = 0;
    Product getResult() { return p; }
protected:
    Product p;
};

class ConcreteBuilder1 : public Builder {
public:
    void buildPartA() override { p.setPartA(1); }
    void buildPartB() override { p.setPartB(2); }
    void buildPartC() override { p.setPartC(3); }
};

class ConcreteBuilder2 : public Builder {
public:
    void buildPartA() override { p.setPartA(7); }
    void buildPartB() override { p.setPartB(8); }
    void buildPartC() override { p.setPartC(9); }
};

class Director {
public:
    void setBuilder(std::shared_ptr<Builder> b) { this->b = b; }
    Product construct(void) {
        b->buildPartA();
        b->buildPartB();
        b->buildPartC();
        return b->getResult();
    }
private:
    std::shared_ptr<Builder> b;
};

int main(int argc, char *argv[]) {
    Director d;
    std::shared_ptr<Builder> b = std::make_shared<ConcreteBuilder1>();
    d.setBuilder(b);
    Product p = d.construct();
    p.show();
    b = std::make_shared<ConcreteBuilder2>();
    d.setBuilder(b);
    p = d.construct();
    p.show();
    return 1;
}