Create Vistor Pattern

Signed-off-by: Junzhuo Du <[email protected]>

BehaviroalPatterns/visitor/Visitor.cxx

@@ -0,0 +1,111 @@
+/*
+ * C++ Design Patterns:
+ * Author: Junzhuo Du [github.com/Junzhuodu]
+ * 2020
+ *
+ */
+
+#include <iostream>
+
+class Element;
+class ConcreteElementA;
+class ConcreteElementB;
+
+class Vistor {
+public:
+    virtual ~Vistor() {}
+
+    virtual void vistorElementA(ConcreteElementA* const element) = 0;
+    virtual void vistorElementB(ConcreteElementB* const element) = 0;
+};
+
+class ConcreteVistor1 : public Vistor {
+public:
+    ~ConcreteVistor1() {}
+
+    void vistorElementA(ConcreteElementA* const element);
+    void vistorElementB(ConcreteElementB* const element);
+};
+
+class ConcreteVistor2 : public Vistor {
+public:
+    ~ConcreteVistor2() {}
+
+    void vistorElementA(ConcreteElementA* const element);
+    void vistorElementB(ConcreteElementB* const element);
+};
+
+class Element {
+public:
+    virtual ~Element() {}
+
+    virtual  void accept(Vistor& v) = 0;
+};
+
+class ConcreteElementA : public Element {
+public:
+    ConcreteElementA(const std::string& data)
+    : data_(data) {}
+    ~ConcreteElementA() {}
+
+    void accept(Vistor& v) {
+        v.vistorElementA(this);
+    }
+
+    std::string getData() {
+        return data_;
+    }
+private:
+    std::string data_;
+};
+
+class ConcreteElementB : public Element {
+public:
+    ConcreteElementB(const std::string& data)
+    : data_(data) {}
+    ~ConcreteElementB() {}
+
+    void accept(Vistor& v) {
+        v.vistorElementB(this);
+    }
+
+    std::string getData() {
+        return data_;
+    }
+private:
+    std::string data_;
+};
+
+void ConcreteVistor1::vistorElementA(ConcreteElementA *const element) {
+    std::cout << "Concrete Vistor 1 : Element A visited." << std::endl;
+    std::cout << "Element A data: " << element->getData() << std::endl;
+}
+
+void ConcreteVistor1::vistorElementB(ConcreteElementB *const element) {
+    std::cout << "Concrete Vistor 1 : Element B visited." << std::endl;
+    std::cout << "Element B data: " << element->getData() << std::endl;
+}
+
+void ConcreteVistor2::vistorElementA(ConcreteElementA *const element) {
+    std::cout << "Concrete Vistor 2 : Element A visited." << std::endl;
+    std::cout << "Element A data: " << element->getData() << std::endl;
+}
+
+void ConcreteVistor2::vistorElementB(ConcreteElementB *const element) {
+    std::cout << "Concrete Vistor 2 : Element B visited." << std::endl;
+    std::cout << "Element B data: " << element->getData() << std::endl;
+}
+
+int main() {
+    ConcreteElementA elementA("Hello");
+    ConcreteElementB elementB("World");
+
+    ConcreteVistor1 vistor1;
+    ConcreteVistor2 vistor2;
+
+    elementA.accept(vistor1);
+    elementA.accept(vistor2);
+
+    elementB.accept(vistor1);
+    elementB.accept(vistor2);
+}