Added chain of responsibility example source code.

examples/behavioral/chain_of_responsibility.cpp

@@ -0,0 +1,95 @@
+#include <iostream>
+#include <memory>
+#include <string>
+
+class Account
+{
+  public:
+    Account(void)
+        : name_("empty account"), balance_(0), successor_()
+    {
+    }
+
+    void setNext(std::shared_ptr<Account> account)
+    {
+      successor_ = account;
+    }
+
+    void pay(float amount)
+    {
+      if (canPay(amount)) {
+        std::cout << "Paid " << amount << " using " << name_ << "."
+                  << std::endl;
+        balance_ -= amount;
+      } else if (successor_) {
+        std::cout << "Cannot pay using " << name_ << ". Proceeding ..."
+                  << std::endl;
+        successor_->pay(amount);
+      } else {
+        std::cerr << "None of the accounts have enough balance." << std::endl;
+      }
+    }
+
+    bool canPay(float amount)
+    {
+      return balance_ >= amount;
+    }
+
+  protected:
+    std::string name_;
+    float balance_;
+    std::shared_ptr<Account> successor_;
+};
+
+class Bank : public Account
+{
+  public:
+    Bank(float balance)
+    {
+      name_ = "bank";
+      balance_ = balance;
+    }
+};
+
+class Paypal : public Account
+{
+  public:
+    Paypal(float balance)
+    {
+      name_ = "paypal";
+      balance_ = balance;
+    }
+};
+
+class Bitcoin : public Account
+{
+  public:
+    Bitcoin(float balance)
+    {
+      name_ = "bitcoin";
+      balance_ = balance;
+    }
+};
+
+int main()
+{
+  // We are going to create the chain: bank->paypal->bitcoin.
+  
+  // First, create the accounts.
+  std::shared_ptr<Account> bank = std::make_shared<Bank>(100);
+  std::shared_ptr<Paypal> paypal = std::make_shared<Paypal>(200);
+  std::shared_ptr<Bitcoin> bitcoin = std::make_shared<Bitcoin>(300);
+
+  // Next, establish the order.
+  bank->setNext(paypal);
+  paypal->setNext(bitcoin);
+
+  // Let's try to pay using the first priority (i.e., the bank).
+  bank->pay(250);
+  // Output:
+  // Cannot pay using bank. Proceeding ...
+  // Cannot pay using paypal. Proceeding ...
+  // Paid 250 using bitcoin.
+
+  return 0;
+}