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POCallback in C++, template member? (2)
 

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  1. POCallback in C++, template member? (2)
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    <p>The following callback class is a generic wrapper to "callable things". I really like its API, which has no templates and is very clean, but under the hood there is some dynamic allocation which I was not able to avoid.</p> <p>Is there any way to get rid of the <strong>new</strong> and <strong>delete</strong> in the code below while maintaining the semantics and API of the callback class? I really wish I could.</p> <hr> <p><strong>Needed stuff:</strong></p> <pre><code>// base class for something we can "call" class callable { public: virtual void operator()() = 0; virtual ~callable() {} }; // wraps pointer-to-members template&lt;class C&gt; class callable_from_object : public callable { public: callable_from_object(C&amp; object, void (C::*method)()) : o(object), m(method) {} void operator()() { (&amp;o -&gt;* m) (); } private: C&amp; o; void (C::*m)(); }; // wraps pointer-to-functions or pointer-to-static-members class callable_from_function : public callable { public: callable_from_function(void (*function)()) : f(function) {} void operator()() { f(); }; private: void (*f)(); }; </code></pre> <hr> <p><strong>The callback class:</strong></p> <pre><code>// generic wrapper for any callable // this is the only class which is exposed to the user class callback : public callable { public: template&lt;class C&gt; callback(C&amp; object, void (C::*method)()) : c(*new callable_from_object&lt;C&gt;(object, method)) {} explicit callback(void (*function)()) : c(*new callable_from_function(function)) {} void operator()() { c(); } ~callback() { std::cout &lt;&lt; "dtor\n"; // check for mem leak delete &amp;c; } private: callable&amp; c; }; </code></pre> <hr> <p><strong>An API example:</strong></p> <pre><code>struct X { void y() { std::cout &lt;&lt; "y\n"; } static void z() { std::cout &lt;&lt; "z\n"; } } x; void w() { std::cout &lt;&lt; "w\n"; } int main(int, char*[]) { callback c1(x, &amp;X::y); callback c2(X::z); callback c3(w); c1(); c2(); c3(); return 0; } </code></pre> <hr> <p>Thanks a lot !! :-)</p>
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    1. USGiovanni Funchal
    1. USGiovanni Funchal
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      1. POCallback in C++, template member? (2)
      1. USGiovanni Funchal
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    1. COsorry to say it still uses templates. Whats wrong with templates?
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    2. COIt uses templates internally, but look at the API in "main". No templates. Nothing is wrong with templates in general, I just fell that they are not needed to implement callbacks. Look at callback c1 for instance, I don't need to say callback<X> etc...
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      1. POCallback in C++, template member? (2)
      1. USGiovanni Funchal
    3. COAlso, not a callback's type should not depend on the called thing. Is the type of callback<A> different from callback<B>? Conceptually not. These are CALLBACKS it does not matter if it calling something in A or B!
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