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POC++ How to call common method from classes without a shared superclass?
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copied!<p>The following code gives a cross/jump label initialization compile errors, of course. But how do I get the effect I'm trying to achieve? That is, only instantiating the class I really need, and then generically calling the method which is common to all classes?</p> <p>Class A and class B are actually not in my code, but in a large library I'm using, so can't be changed to help. They are NOT children of a superclass (which would solve the problem). </p> <p>Both real classes handle similar data, so are compatible in the way illustrated below with the filter() method. I know a number of ugly C hacks which might be used to make it work, but I am looking for C++ idiomatic solutions.</p> <p>In the real problem, there is a lot more code and many more cases, and the constructor and class methods are resource intensive, so I can't just init all possible classes "just in case" and then pick the right filter() method with the switch ().</p> <pre><code>#include <string> #include <iostream> class A { public: std::string msg; A(std::string s) { msg = s;} void filter() { std::cout << "Message A = " << msg << std::endl;} }; class B { public: std::string msg; B(std::string s) { msg = s;} void filter() { std::cout << "The B message: " << msg << std::endl;} }; int main() { int type = 1; switch (type) { case 1: A f("hi from A"); break; case 2: B f("hello from B"); break; } f.filter(); } </code></pre> <p>EDIT: Based on @stefan's answer, I revised my code to look like what's below. I haven't tried it in the real situation yet, but I believe it will work. (Thanks all!)</p> <pre><code>#include <string> #include <iostream> class A { public: std::string msg; A(std::string s) { msg = s;} void filter() { std::cout << "Message A = " << msg << std::endl;} }; class B { public: std::string msg; B(std::string s) { msg = s;} void filter() { std::cout << "The B message: " << msg << std::endl;} }; template <class F> void doFilterStuff(std::string msg) { F f(msg); f.filter(); } int main() { for (int i=1; i<4; i++) { std::cout << "Type = " << i << std::endl; switch (i) { case 1: doFilterStuff<A>("hi from A"); break; case 2: doFilterStuff<B>("hello from B"); break; default: std::cout << "Throwing an error exception" << std::endl; } } } </code></pre>

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