{"id":1854,"date":"2025-01-25T20:26:20","date_gmt":"2025-01-25T20:26:20","guid":{"rendered":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/?page_id=1854"},"modified":"2025-01-25T21:17:06","modified_gmt":"2025-01-25T21:17:06","slug":"output-of-user-defined-types","status":"publish","type":"page","link":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/topics\/c-details\/i-o-streams\/output-of-user-defined-types\/","title":{"rendered":"Output of User-Defined Types"},"content":{"rendered":"\n

<\/span>Output of User-Defined Types<\/span><\/h2>\n\n\n\n

Imagine you have written a class Person<\/code><\/strong>:<\/p>\n\n\n\n

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\/\/<\/span><\/span>\n\/\/  Person.h<\/span><\/span>\n\/\/  iostreams - User-defined types<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 9\/4\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#ifndef<\/span> Person_h<\/span><\/span>\n#define<\/span> Person_h<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n<\/span>\nclass<\/span> <\/span>Person<\/span><\/span>\n{<\/span><\/span>\npublic:<\/span><\/span>\n  \/\/ Constructor<\/span><\/span>\n  <\/span>Person<\/span>(<\/span>const<\/span> <\/span>std<\/span>::<\/span>string<\/span> <\/span>&<\/span>nm<\/span>,<\/span><\/span>\n         <\/span>const<\/span> <\/span>std<\/span>::<\/span>string<\/span> <\/span>&<\/span>street<\/span> = <\/span>""<\/span>, <\/span><\/span>\n         <\/span>const<\/span> <\/span>std<\/span>::<\/span>string<\/span> <\/span>&<\/span>town<\/span> = <\/span>""<\/span>,<\/span><\/span>\n         <\/span>const<\/span> <\/span>std<\/span>::<\/span>string<\/span> <\/span>&<\/span>state<\/span> = <\/span>""<\/span>,<\/span><\/span>\n         <\/span>int<\/span> <\/span>a<\/span> = -<\/span>1<\/span>);<\/span><\/span>\n  <\/span><\/span>\n  \/\/ Access member functions<\/span><\/span>\n  <\/span>const<\/span> <\/span>std<\/span>::<\/span>string<\/span> <\/span>&<\/span>getName<\/span>() <\/span>const<\/span> { <\/span>return<\/span> m_name; }<\/span><\/span>\n  <\/span>const<\/span> <\/span>std<\/span>::<\/span>string<\/span> <\/span>&<\/span>getStreet<\/span>() <\/span>const<\/span> { <\/span>return<\/span> m_street; }<\/span><\/span>\n  <\/span>const<\/span> <\/span>std<\/span>::<\/span>string<\/span> <\/span>&<\/span>getTown<\/span>() <\/span>const<\/span> { <\/span>return<\/span> m_town; }<\/span><\/span>\n  <\/span>const<\/span> <\/span>std<\/span>::<\/span>string<\/span> <\/span>&<\/span>getState<\/span>() <\/span>const<\/span> { <\/span>return<\/span> m_state; }<\/span><\/span>\n  <\/span>const<\/span> <\/span>int<\/span> <\/span>getAge<\/span>() <\/span>const<\/span> { <\/span>return<\/span> m_age; }<\/span><\/span>\n  <\/span><\/span>\n  \/\/ Mutator member functions<\/span><\/span>\n  <\/span>void<\/span> <\/span>setStreet<\/span>(<\/span>const<\/span> <\/span>std<\/span>::<\/span>string<\/span> <\/span>&<\/span>street<\/span>) { m_street = street; }<\/span><\/span>\n  <\/span>void<\/span> <\/span>setTown<\/span>(<\/span>const<\/span> <\/span>std<\/span>::<\/span>string<\/span> <\/span>&<\/span>town<\/span>) { m_town = town; }<\/span><\/span>\n  <\/span>void<\/span> <\/span>setState<\/span>(<\/span>const<\/span> <\/span>std<\/span>::<\/span>string<\/span> <\/span>&<\/span>state<\/span>) { m_state = state; }<\/span><\/span>\n  <\/span>void<\/span> <\/span>setAge<\/span>(<\/span>int<\/span> <\/span>age<\/span>) { m_age = age; }<\/span><\/span>\n<\/span>\nprivate:<\/span><\/span>\n  <\/span>std<\/span>::string m_name;<\/span><\/span>\n  <\/span>std<\/span>::string m_street;<\/span><\/span>\n  <\/span>std<\/span>::string m_town;<\/span><\/span>\n  <\/span>std<\/span>::string m_state;<\/span><\/span>\n  <\/span>int<\/span>  m_age;<\/span><\/span>\n};<\/span><\/span>\n<\/span>\n#endif<\/span> \/* Person_h *\/<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
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You’d like to be able to say something like:<\/p>\n\n\n\n
Person p(\"Fred Bloggs\");\n\/\/ ...\ncout << p;<\/strong><\/code><\/pre>\n\n\n\n
How can you accomplish this?<\/p>\n<\/div>\n<\/div>\n\n\n\n
<\/span>What’s required for the implementation of an overloaded operator <<<\/code><\/strong>  for class Person<\/code><\/strong>?<\/span><\/h3>\n\n\n\n
Look at the above expression:<\/p>\n\n\n\n
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  • operator <<<\/code><\/strong> is a binary operator<\/li>\n\n\n\n
  • its left-hand operand is a type ostream<\/code><\/strong><\/li>\n\n\n\n
  • its right-hand operand is a type Person<\/code><\/strong><\/li>\n\n\n\n
  • you’d like to be able to string this expression together with others:
    cout << \"Person #\" << id << \" is: \" << p<\/code><\/strong> 
    (which associates left to right.)<\/li>\n<\/ul>\n\n\n\n
    <\/span>Questions:<\/em><\/span><\/h4>\n\n\n\n
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    • Can the resulting overloaded operator <<<\/code><\/strong> function be a member function of the class Person<\/code><\/strong>?<\/li>\n\n\n\n
    • What should its argument list contain?
      How many arguments?  What types?  All const<\/strong><\/code>?<\/li>\n\n\n\n
    • What should its return type be?<\/li>\n<\/ul>\n\n\n\n
      <\/span>Answers:<\/em><\/span><\/h4>\n\n\n\n