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copied!<p>I once solved this by simulating .NET delegates:</p> <pre><code>template<typename T> class Delegate { //static_assert(false, "T must be a function type"); }; template<typename ReturnType> class Delegate<ReturnType()> { private: class HelperBase { public: HelperBase() { } virtual ~HelperBase() { } virtual ReturnType operator()() const = 0; virtual bool operator==(const HelperBase& hb) const = 0; virtual HelperBase* Clone() const = 0; }; template<typename Class> class Helper : public HelperBase { private: Class* m_pObject; ReturnType(Class::*m_pMethod)(); public: Helper(Class* pObject, ReturnType(Class::*pMethod)()) : m_pObject(pObject), m_pMethod(pMethod) { } virtual ~Helper() { } virtual ReturnType operator()() const { return (m_pObject->*m_pMethod)(); } virtual bool operator==(const HelperBase& hb) const { const Helper& h = static_cast<const Helper&>(hb); return m_pObject == h.m_pObject && m_pMethod == h.m_pMethod; } virtual HelperBase* Clone() const { return new Helper(*this); } }; HelperBase* m_pHelperBase; public: template<typename Class> Delegate(Class* pObject, ReturnType(Class::*pMethod)()) { m_pHelperBase = new Helper<Class>(pObject, pMethod); } Delegate(const Delegate& d) { m_pHelperBase = d.m_pHelperBase->Clone(); } Delegate(Delegate&& d) { m_pHelperBase = d.m_pHelperBase; d.m_pHelperBase = nullptr; } ~Delegate() { delete m_pHelperBase; } Delegate& operator=(const Delegate& d) { if (this != &d) { delete m_pHelperBase; m_pHelperBase = d.m_pHelperBase->Clone(); } return *this; } Delegate& operator=(Delegate&& d) { if (this != &d) { delete m_pHelperBase; m_pHelperBase = d.m_pHelperBase; d.m_pHelperBase = nullptr; } return *this; } ReturnType operator()() const { (*m_pHelperBase)(); } bool operator==(const Delegate& d) const { return *m_pHelperBase == *d.m_pHelperBase; } bool operator!=(const Delegate& d) const { return !(*this == d); } }; </code></pre> <p>You can use it much like .NET delegates:</p> <pre><code>class A { public: void M() { ... } }; class B { public: void M() { ... } }; A a; B b; Delegate<void()> d = Delegate<void()>(&a, &A::M); d(); // calls A::M d = Delegate<void()>(&b, &B::M); d(); // calls B::M </code></pre> <p>This works with methods that have no arguments. If you can use C++11, you can modify it to use variadic templates to handle any number of parameters. Without C++11, you need to add more Delegate specializations to handle specific numbers of parameters:</p> <pre><code>template<typename ReturnType, typename Arg1> class Delegate<ReturnType(Arg1)> { ... }; template<typename ReturnType, typename Arg1, typename Arg2> class Delegate<ReturnType(Arg1, Arg2)> { ... }; </code></pre> <p>With this Delegate class you can also emulate .NET events, which are based on delegates.</p>

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