访问者模式

#include <iostream>
#include <memory>

class ConcreteComponent1;
class ConcreteComponent2;

class Visitor {
public:
    virtual void visitconcretecomponent1(ConcreteComponent1 *cc1) = 0;
    virtual void visitconcretecomponent2(ConcreteComponent2 *cc2) = 0;
};

class Component {
public:
    virtual void accept(std::shared_ptr<Visitor> v) = 0;
};

class ConcreteComponent1 : public Component {
public:
    void accept(std::shared_ptr<Visitor> cv) {
        cv->visitconcretecomponent1(this);
    }
    int data1() { return 1; }
    std::string data2() { return "2"; }
};

class ConcreteComponent2 : public Component {
public:
    void accept(std::shared_ptr<Visitor> cv) {
        cv->visitconcretecomponent2(this);
    }
    int data1() { return 3; }
    std::string data2() { return "4"; }
};

class ConcreteVisitor1 : public Visitor {
public:
    void visitconcretecomponent1(ConcreteComponent1 *cc) override {
        std::cout << "In ConcreteVisitor1 visitconcretecomponent1. The data1 is " << cc->data1() << std::endl;
        std::cout << "In ConcreteVisitor1 visitconcretecomponent1. The data2 is " << cc->data2() << std::endl;
    }
    void visitconcretecomponent2(ConcreteComponent2 *cc) override {
        std::cout << "In ConcreteVisitor1 visitconcretecomponent2. The data1 is " << cc->data1() << std::endl;
        std::cout << "In ConcreteVisitor1 visitconcretecomponent2. The data2 is " << cc->data2() << std::endl;
    }
};

class ConcreteVisitor2 : public Visitor {
public:
    void visitconcretecomponent1(ConcreteComponent1 *cc) override {
        std::cout << "In ConcreteVisitor2 visitconcretecomponent1. The data2 is " << cc->data2() << std::endl;
        std::cout << "In ConcreteVisitor2 visitconcretecomponent1. The data1 is " << cc->data1() << std::endl;
    }
    void visitconcretecomponent2(ConcreteComponent2 *cc) override {
        std::cout << "In ConcreteVisitor2 visitconcretecomponent2. The data2 is " << cc->data2() << std::endl;
        std::cout << "In ConcreteVisitor2 visitconcretecomponent2. The data1 is " << cc->data1() << std::endl;
    }
};

int main(int argc, char *argv[]) {
    std::shared_ptr<Component> cc1 = std::make_shared<ConcreteComponent1>();
    std::shared_ptr<Component> cc2 = std::make_shared<ConcreteComponent2>();
    std::shared_ptr<Visitor> v1 = std::make_shared<ConcreteVisitor1>();
    std::shared_ptr<Visitor> v2 = std::make_shared<ConcreteVisitor2>();
    cc1->accept(v1);
    cc2->accept(v2);
    return 1;
}