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POOverriding operator<< for console output doesn't work for member variables
 

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    <p>I have a class MyList that overrides the <code>&lt;&lt;</code> operator to be able to log itself to the console:</p> <pre><code>class MyList { public: vector&lt;int&gt; *numbers; }; ostream&amp; operator&lt;&lt;(ostream&amp; os, MyList&amp; l); </code></pre> <p>Implementation:</p> <pre><code>ostream&amp; operator&lt;&lt;(ostream&amp; os, MyList&amp; l) { for (int i = 0; i &lt; l.numbers-&gt;size(); i++) { os &lt;&lt; l.numbers-&gt;at(i); } return os; } </code></pre> <p>In an other class I have a member variable of type MyList and I can't print it to the console. Interestingly a local MyList variable works fine:</p> <pre><code>class A { public: MyList list; void someMethod() const; }; </code></pre> <p>Implementation:</p> <pre><code>void A::someMethod() const { MyList local; // Set up local list. cout &lt;&lt; "Local:" &lt;&lt; local; // OK! cout &lt;&lt; "Member:" &lt;&lt; list; // ERROR! } </code></pre> <p><strong>This is the error message:</strong></p> <pre><code>Invalid operands to binary expression ('basic_ostream&lt;char, std::__1::char_traits&lt;char&gt;&gt;' and 'const MyList') </code></pre> <p>Xcode's auto-fix recommends to reference <code>list</code>:</p> <pre><code>cout &lt;&lt; "Member:" &lt;&lt; &amp;list; </code></pre> <p>This will compile, but (obviously) it prints the adress of <code>list</code> and not my content. I don't understand what the difference is between those two variables in regards to the <code>&lt;&lt;</code> operator. Could anybody explain?</p>
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    1. CODue to the **missing semicolon** after the definition of class A, it is unlikely that the compiler would get as far as you claim, before emitting some error diagnostic. Is this really your *real code*? And if it isn't, how you think we can infer what you real code is?
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      1. USCheers and hth. - Alf
 

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