Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p><em>Note:</em> You might want to look at the <a href="https://stackoverflow.com/q/4421706/140719">operator overloading FAQ</a>. </p> <hr> <p>Binary operators can either be members of their left-hand argument's class or free functions. (Some operators, like assignment, must be members.) Since the stream operators' left-hand argument is a stream, stream operators either have to be members of the stream class or free functions. The canonical way to implement <code>operator&lt;&lt;</code> for any type is this: </p> <pre><code>std::ostream&amp; operator&lt;&lt;(std::ostream&amp; os, const T&amp; obj) { // stream obj's data into os return os; } </code></pre> <p>Note that it is <strong><em>not</em></strong> a member function. Also note that it takes the object to stream per <code>const</code> reference. That's because you don't want to copy the object in order to stream it and you don't want the streaming to alter it either. </p> <hr> <p>Sometimes you want to stream objects whose internals are not accessible through their class' public interface, so the operator can't get at them. Then you have two choices: Either put a public member into the class which does the streaming</p> <pre><code>class T { public: void stream_to(std::ostream&amp;) const {os &lt;&lt; obj.data_;} private: int data_; }; </code></pre> <p>and call that from the operator: </p> <pre><code>inline std::ostream&amp; operator&lt;&lt;(std::ostream&amp; os, const T&amp; obj) { obj.stream_to(os); return os; } </code></pre> <p>or make the operator a <code>friend</code> </p> <pre><code>class T { public: friend std::ostream&amp; operator&lt;&lt;(std::ostream&amp;, const T&amp;); private: int data_; }; </code></pre> <p>so that it can access the class' private parts: </p> <pre><code>inline std::ostream&amp; operator&lt;&lt;(std::ostream&amp; os, const T&amp; obj) { os &lt;&lt; obj.data_; return os; } </code></pre>
    singulars
    1. This table or related slice is empty.
    1. PO'friend' functions and << operator overloading: What is the proper way to overload an operator for a class?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USCommunity
    1. USsbi
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO'friend' functions and << operator overloading: What is the proper way to overload an operator for a class?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. CONice, complete answer.
      singulars
      1. PO
      1. USCrazy Eddie
    2. COAccess the class' private parts - Rawr. J/K, thank you very much, yet one question remains: I deleted all mentions to the overload on the header file... yet I get the following (and only) error. `binary '<<' : no operator found which takes a right-hand operand of type 'Score' (or there is no acceptable conversion)` How come my test, in main(), can't find the appropriate overload? (it's not the includes).
      singulars
      1. PO
      1. USFrancisco P.
    3. COYou should put the declaration of the `operator<<` right with the definition of your class: that is in the same header and in the same namespace. This way you won't forget to include it and you the compiler will be able to pick it up when looking for acceptable overloads.
      singulars
      1. PO
      1. USMatthieu M.
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload