command.cpp

#include <iostream>
#include <vector>

using namespace std;

struct BankAccount {
  int balance{0};
  int overdraft_limit{-500};

  void deposit(int amount) {
    balance += amount;
    cout << "deposited " << amount << ", balance is now " << balance << "\n";
  }

  void withdraw(int amount) {
    if (balance - amount >= overdraft_limit) {
      balance -= amount;
      cout << "withdrew " << amount << ", balance is now " << balance << "\n";
    }
  }

  friend std::ostream &operator<<(std::ostream &os,
                                  const BankAccount &account) {
    os << "balance: " << account.balance;
    return os;
  }
};

struct Command {
  virtual void call() = 0;
};

struct BankAccountCommand : Command {
  BankAccount &account;
  enum Action { deposit, withdraw } action;
  int amount;

  BankAccountCommand(BankAccount &account, Action action, int amount)
      : account{account}, action{action}, amount{amount} {}

  void call() override {
    switch (action) {
    case deposit:
      account.deposit(amount);
      break;
    case withdraw:
      account.withdraw(amount);
      break;
    }
  }
};

int main() {
  BankAccount ba;
  vector<BankAccountCommand> commands{
      BankAccountCommand{ba, BankAccountCommand::deposit, 100},
      BankAccountCommand{ba, BankAccountCommand::withdraw, 200},
  };
  cout << ba << endl;
  for (auto &cmd : commands) {
    cmd.call();
  }
  cout << ba << endl;

  return 0;
}