title: error: no match for 'operator>>'
body: <p>I'm reading C++ Primer 5th Edition when i came to this part. It's a code it provided that I have to use but I keep getting</p>
  
  <blockquote>
    <p>error: no match for <code>'operator&gt;&gt;'</code> (operand types are <code>std::istream</code> {aka <code>std::basic_istream&lt;char&gt;}</code> and <code>Sales_item</code>)</p>
  </blockquote>
  
  <p>on line <code>std::cin &gt;&gt; book;</code></p>
  
  <p>I tried looking it up and rewriting the code but I can't get it to work so I need help to fix this problem.</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include "Sales_item.h"
  
  
  int main()
  {
      Sales_item book;
      // read ISBN, number of copes sold, and sales price
      std::cin &gt;&gt; book;
       // write ISBN, number of copies sold, total revenue, and average price
      std::cout &lt;&lt; book &lt;&lt; std::endl;
      return 0;
  }
  </code></pre>