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| <h3 class="sectionHead"><span class="titlemark">1.6 </span> <a |
| id="x11-300001.6"></a>The <span |
| class="pcrr7t-">VError </span>class</h3> |
| <!--l. 3--><p class="noindent" >The <span class="obeylines-h"><span class="verb"><span |
| class="pcrr7t-">VError</span></span></span> class is the class thrown by the VIPS |
| C++ API when an error is detected. It is derived from |
| <span class="obeylines-h"><span class="verb"><span |
| class="pcrr7t-">std::exception</span></span></span> in the usual way. |
| <!--l. 6--><p class="noindent" > |
| <h4 class="subsectionHead"><span class="titlemark">1.6.1 </span> <a |
| id="x11-310001.6.1"></a>Constructors</h4> |
| <!--l. 8--><p class="noindent" >There are two constructors for <span class="obeylines-h"><span class="verb"><span |
| class="pcrr7t-">VError</span></span></span>: |
| <div class="verbatim" id="verbatim-41"> |
| VError( std::string str ); |
|  <br />VError(); |
| </div> |
| <!--l. 13--><p class="nopar" > |
| <!--l. 15--><p class="indent" > The first form creates an error object initialised with the |
| specified string, the last form creates an empty error |
| object. |
| <!--l. 18--><p class="noindent" > |
| <h4 class="subsectionHead"><span class="titlemark">1.6.2 </span> <a |
| id="x11-320001.6.2"></a>Projection functions</h4> |
| <!--l. 20--><p class="noindent" >A function gives access to the string held by <span class="obeylines-h"><span class="verb"><span |
| class="pcrr7t-">VError</span></span></span>: |
| |
| |
| |
| <div class="verbatim" id="verbatim-42"> |
| const char ⋆what(); |
| </div> |
| <!--l. 24--><p class="nopar" > |
| <!--l. 26--><p class="indent" > You can also send to an <span class="obeylines-h"><span class="verb"><span |
| class="pcrr7t-">ostream</span></span></span>. |
| <div class="verbatim" id="verbatim-43"> |
| std::ostream& operator<<( |
|  <br />    std::ostream&, const error& ); |
| </div> |
| <!--l. 31--><p class="nopar" > |
| <!--l. 33--><p class="noindent" > |
| <h4 class="subsectionHead"><span class="titlemark">1.6.3 </span> <a |
| id="x11-330001.6.3"></a>Computing with <span |
| class="pcrr7t-">VError</span></h4> |
| <!--l. 35--><p class="noindent" >Two member functions let you append elements to an |
| error: |
| |
| |
| |
| <div class="verbatim" id="verbatim-44"> |
| VError &app( std::string txt ); |
|  <br />VError &app( const int i ); |
| </div> |
| <!--l. 40--><p class="nopar" > |
| <!--l. 42--><p class="indent" > For example: |
| <div class="verbatim" id="verbatim-45"> |
| VError wombat; |
|  <br />int n = 12; |
|  <br /> |
|  <br />wombat.app( "possum: no more than " ). |
|  <br />app( n ).app( " elements\n" ); |
|  <br />throw( wombat ); |
| </div> |
| <!--l. 51--><p class="nopar" > |
| <!--l. 53--><p class="noindent" >will throw a <span class="obeylines-h"><span class="verb"><span |
| class="pcrr7t-">VError</span></span></span> with a diagnostic of: |
| |
| |
| |
| <div class="verbatim" id="verbatim-46"> |
| possum: no more than 12 elements |
| </div> |
| <!--l. 58--><p class="nopar" > |
| <!--l. 60--><p class="indent" > The member function <span class="obeylines-h"><span class="verb"><span |
| class="pcrr7t-">perror()</span></span></span> prints the error |
| message to <span class="obeylines-h"><span class="verb"><span |
| class="pcrr7t-">stdout</span></span></span> and exits with a code of 1. |
| <div class="verbatim" id="verbatim-47"> |
| void perror( const char ⋆ ); |
|  <br />void perror(); |
| </div> |
| <!--l. 66--><p class="nopar" > |
| <!--l. 68--><p class="noindent" > |
| <h4 class="subsectionHead"><span class="titlemark">1.6.4 </span> <a |
| id="x11-340001.6.4"></a>Convenience function</h4> |
| <!--l. 70--><p class="noindent" >The convenience function <span class="obeylines-h"><span class="verb"><span |
| class="pcrr7t-">verror</span></span></span> creates an <span class="obeylines-h"><span class="verb"><span |
| class="pcrr7t-">VError</span></span></span> |
| with the specified error string, and throws it. If you pass <span class="obeylines-h"><span class="verb"><span |
| class="pcrr7t-">""</span></span></span> |
| for the string, verror uses the contents of the VIPS error |
| buffer instead. |
| |
| |
| |
| <div class="verbatim" id="verbatim-48"> |
| extern void verror( std::string str = "" ); |
| </div> |
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