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POInheriting and overriding ostream operator in C++
 

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    <p>I've been trying to find an answer to this, but no one seems to have exactly the same problem as I do.</p> <p>I am working with several derived classes. The ostream operator &lt;&lt; for each of these should print out some things common to each, and some things specific to each. Later on, I would like to further derive from these derived classes, and again the new derived classes need to print out some things that are in the "generations" above them.<br> For example:</p> <p>The Base class .h file</p> <pre><code>class Base { int FirstClassNumber; //The declaration I'm currently working with, that a friend gave me //I'm pretty sure my problem lies here. public: friend ostream&amp; operator &lt;&lt; (ostream&amp; os, const Base &amp;base) { base &lt;&lt; os ; return os; } virtual void operator &lt;&lt; (ostream&amp; os) const = 0; }; </code></pre> <p>The Base.cpp file includes these lines:</p> <pre><code>void Base::operator &lt;&lt; (ostream&amp; os) { os &lt;&lt; FirstClassNumber; } </code></pre> <p>Then I derive: (FirstDerived.h)</p> <pre><code>class FirstDerived : Public Base { int SecondClassNumber; }; </code></pre> <p>FirstDerived.cpp:</p> <pre><code>FirstDerived::operator &lt;&lt; (ostream&amp; os) { os &lt;&lt; "The first Number is: //This is the line that isn't working - someone else gave me this syntax &lt;&lt; Base::operator&lt;&lt; &lt;&lt; "The second number is" &lt;&lt; SecondClassNumber; } </code></pre> <p>Then I want to derive:</p> <pre><code>class SecondDerived: Public FirstDerived { int ThirdClassNumber; }; </code></pre> <p>Second.cpp:</p> <pre><code>FirstDerived::operator &lt;&lt; (ostream&amp; os) { os &lt;&lt; FirstDerived::operator&lt;&lt; &lt;&lt; "The third number is " &lt;&lt; ThirdClassNumber; } </code></pre> <p>I think the problem is most likely either the declaration in the very start of the program, or the lines like <code>Base::operator&lt;&lt;</code>.</p> <p>Another possibility is that I'm not redeclaring it in the .h file of every inherited class. Should I be, and if so what syntax should I use? </p> <p>It was suggested to me to use the <code>static_cast</code> method, but my professor (the one who wrote the assignment, and therefore won't give us too much help with it) said that there's a better way to do it. Any suggestions?</p>
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    1. CO"I think the problem is most likely..." - what symptoms are you observing? Compilation error? Line, message? Or undesired run-time behaviour? If so what, and what did you expect?
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