template_example.cpp

// template_example.cpp

#include <algorithm>
#include <cstddef>
#include <iostream>
#include <vector>

#include "delegate.hpp"

template <typename T>
class Base {
 public:
  virtual ~Base() = default;

  Delegate<void(const T&, std::size_t)> OnItemAdded;

  virtual bool add(const T& value) {
    items_.push_back(value);
    OnItemAdded(value, items_.size());
    return true;
  }

  const std::vector<T>& items() const { return items_; }

 protected:
  bool contains(const T& value) const { return std::find(items_.begin(), items_.end(), value) != items_.end(); }

 private:
  std::vector<T> items_;
};

class IntContainer : public Base<int> {
 public:
  bool add(const int& value) override {
    if (this->contains(value)) {
      std::cout << value << " already exists, skip" << '\n';
      return false;
    }

    return Base<int>::add(value);
  }
};

class Printer {
 public:
  void onItemAdded(const int& value, std::size_t size) {
    std::cout << "added number: " << value << ", current size: " << size << '\n';
  }
};

int main() {
  IntContainer container;

  Printer printer;
  container.OnItemAdded.add(&printer, &Printer::onItemAdded);

  container.add(10);
  container.add(20);
  container.add(10);
  container.add(30);

  std::cout << "final values:";
  for (int value : container.items()) {
    std::cout << ' ' << value;
  }
  std::cout << '\n';

  return 0;
}