Composite.cpp

#include <algorithm>
#include <iostream>
#include <list>
#include <string>

class Component {
  
 protected:
  Component *parent_;
  
 public:
  virtual ~Component() {}
  void SetParent(Component *parent) {
    this->parent_ = parent;
  }
  Component *GetParent() const {
    return this->parent_;
  }
  
  virtual std::string Operation() const = 0;
};

class Leaf : public Component {
 public:
  std::string Operation() const override {
    return "Leaf";
  }
};

class Composite : public Component {
  
 protected:
  std::list<Component *> children_;

 public:
  
  void Add(Component *component) override {
    this->children_.push_back(component);
    component->SetParent(this);
  }
  
  void Remove(Component *component) override {
    children_.remove(component);
    component->SetParent(nullptr);
  }
  bool IsComposite() const override {
    return true;
  }
  
  std::string Operation() const override {
    std::string result;
    for (const Component *c : children_) {
      if (c == children_.back()) {
        result += c->Operation();
      } else {
        result += c->Operation() + "+";
      }
    }
    return "Branch(" + result + ")";
  }
};

void ClientCode(Component *component) {
  std::cout << "RESULT: " << component->Operation();
}


void ClientCode2(Component *component1, Component *component2) {
  
  if (component1->IsComposite()) {
    component1->Add(component2);
  }
  std::cout << "RESULT: " << component1->Operation();
  
}