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POCan I create anonymous classes in C++ and capture the outside variables like in Java?
 

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  1. POCan I create anonymous classes in C++ and capture the outside variables like in Java?
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    <p>In Java, when I need a callback function, I have to implement an anonymous class. Inside the anonymous class, I can access the outside variables if they're <code>final</code>.</p> <p>Now I'm doing the same thing in C++. I understand that C++ lambda works better but sometimes I need to pass in many functions where with anonymous classes, I only need to pass in one instance.</p> <p>I tried the following example. It works with GCC 4.3.4.</p> <pre><code>class IA { public: virtual int f(int x) = 0; }; int main() { class : public IA { int f(int x) { return x + 1; } } a; doFancyWork(&amp;a); return 0; } </code></pre> <p>Is it possible to capture the outside variables like this?</p> <pre><code>int main() { int y = 100; // mark y as final if possible class : public IA { int f(int x) { return x + y; } } a; return 0; } </code></pre> <p>UPDATE:</p> <p>The second example won't compile. The errors are here,</p> <pre><code>prog.cpp: In member function ‘virtual int main()::&lt;anonymous class&gt;::f(int)’: prog.cpp:9: error: use of ‘auto’ variable from containing function prog.cpp:7: error: ‘int y’ declared here prog.cpp: In function ‘int main()’: prog.cpp:7: warning: unused variable ‘y’ </code></pre> <p>UPDATE:</p> <p>I just realized a few more problems in doing this:</p> <ul> <li>I cannot write a constructor because the class doesn't have a name</li> <li>initializer list doesn't allow inheritance.</li> <li>any change to make it compile makes the code unreadable.</li> </ul> <p>I think I have to move away from anonymous classes.</p>
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    1. CODoes it compile and run?
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    2. COThe first example compiles. (tested with http://ideone.com/) The second doesn't.
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    3. COTo capture the value of `y`, you would need to add a member `y` to your anonymous class. (Or a lambda automatically handles "capturing" in exactly that way.)
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