Delegates: Difference between revisions

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@@ Line 158: / Line 158: @@
             Delegator_Operation( theDelegator, 3, del2));
     return 0;
+}</lang>
+=={{header|C++}}==
+<lang Cpp>#include <boost/shared_ptr.hpp>
+#include <string>
+#include <iostream>
+// interface
+class IDelegate
+{
+public:
+    virtual std::string Thing()
+    {
+        return "default implementation";
+    }
+protected:
+    IDelegate() {}
+};
+// Does not handle Thing
+class DelegateA : public IDelegate
+{
+};
+// Handles Thing
+class DelegateB : public IDelegate
+{
+    std::string Thing()
+    {
+        return "delegate implementation";
+    }
+};
+class Delegator
+{
+public:
+    std::string Operation()
+    {
+        if(Delegate)
+            return Delegate->Thing();
+        else
+            return "no implementation";
+    }
+    boost::shared_ptr<IDelegate> Delegate;
+};
+int main()
+{
+    boost::shared_ptr<DelegateA> delegateA(new DelegateA());
+    boost::shared_ptr<DelegateB> delegateB(new DelegateB());
+    Delegator delegator;
+    // No delegate
+    std::cout << delegator.Operation() << std::endl;
+    // Delegate doesn't handle "Thing"
+    delegator.Delegate = delegateA;
+    std::cout << delegator.Operation() << std::endl;
+    // Delegate handles "Thing"
+    delegator.Delegate = delegateB;
+    std::cout << delegator.Operation() << std::endl;
 }</lang>