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184 lines
5.6 KiB
184 lines
5.6 KiB
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<TITLE>Types and Related Topics</TITLE>
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<TH COLSPAN="3" ALIGN="center">Python Bindings for KDE (PyKDE-3.16.0)</TH>
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</DIV>
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<H1>Types and Related Topics</H1>
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<H2>Static Member Functions</H2>
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<P>
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Static member functions are implemented as Python class functions.
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For example the C++ static member function
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<TT CLASS="LITERAL" >TQObject::connect()</TT>
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is called from Python as
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<TT CLASS="LITERAL">TQObject.connect()</TT> or
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<TT CLASS="LITERAL">self.connect()</TT>
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if called from a sub-class of
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<TT CLASS="LITERAL">TQObject</TT>.
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</P>
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<h2>None and NULL</h2>
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<P>Throughout the bindings, the
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<TT CLASS="LITERAL">None</TT>
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value can be specified wherever
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<TT CLASS="LITERAL">NULL</TT>
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is acceptable to the underlying C++ code.</P>
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<P >Equally,
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<TT CLASS="LITERAL">NULL</TT>
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is converted to
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<TT CLASS="LITERAL">None</TT>
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whenever it is returned by the underlying C++ code
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</P>
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<h2>Enumerated Types</H2>
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<P>
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Enumerated types are implemented as a set of simple variables corresponding to
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the separate enumerated values.
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</P>
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<P>
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When using an enumerated value the name of the class (or a sub-class) in which
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the enumerated type was defined in must be included. For example:
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</P>
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<TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" >
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<TR>
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<TD>
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<PRE CLASS="PROGRAMLISTING">
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TQt.SolidPattern
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TQWidget.TabFocus
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TQFrame.TabFocus
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</PRE>
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</TD>
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</TR>
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</TABLE>
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<H2>Namespaces</H2>
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<P>
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The C++ code in KDE makes extensive use of namespaces (especially in the kio, kjs,
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tdehtml, tdefile, and tdeparts modules). In PyKDE, namespaces are treated as a "superclass".
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For example, "from tdeparts import KParts" will import the KParts namespace and all
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its members. To reference a class in the namespace, use <namespace name>..<classname>,
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for example, KParts.ReadOnlyPart. It isn't necessary to import the <classname> (ReadOnlyPart
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in the example).
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</P>
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<h2>Return and Argument Types</h2>
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<p>
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Some return types or argument types may be different than those in the C++ KDE libs. This is
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done for convenience (eg returning/taking Python lists or dicts), because arguments are
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scalar (non-object) types passed by reference (eg int*, bool&), or because there is no
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way to express the C++ type in Python (eg template types)
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</p>
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<p>
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Please check the <a href="docs.html">Class Reference Docs</a> which list all classes
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and methods in Python format.
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</p>
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<h2>Version Information</h2><h4><i>New in PyKDE-3.11</i></h4>
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<p>
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PyKDE provides methods for determining both the KDE version being run and the PyKDE
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version being run. The version methods are:
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</p>
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<table border="0" bgcolor="#E0E0E0" width="100%">
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<tr>
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<th align = "left" width = "20%"><u>return type</u></th>
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<th align = "left" width = "20%"><u>KDE</u></th>
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<th align = "center" width = "10%"><u>Example</u></th>
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<th></th>
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<th align = "left" width = "20%"><u>PyKDE</u></th>
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<th align = "center" width = "20%"><u>Example</u></th>
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</tr>
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<tr>
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<td>int</td>
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<td>KDE.versionMajor ()</td>
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<td align = "center">3</td>
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<td></td>
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<td>PyKDE.versionMajor ()</td>
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<td align = "center">3</td>
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</tr>
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<tr>
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<td>int</td>
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<td>KDE.versionMinor ()</td>
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<td align = "center">1</td>
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<td></td>
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<td>PyKDE.versionMinor ()</td>
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<td align = "center">8</td>
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</tr>
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<tr>
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<td>int</td>
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<td>KDE.versionRelease ()</td>
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<td align = "center">4</td>
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<td></td>
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<td>PyKDE.versionRelease ()</td>
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<td align = "center">0</td>
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</tr>
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<tr>
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<td>string</td>
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<td>KDE.versionString ()</td>
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<td align = "center">"3.1.4"</td>
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<td></td>
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<td>PyKDE.versionString ()</td>
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<td align = "center">"3.11.0"</td>
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</tr>
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</table>
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<h2>Abstract Classes and Pure Virtual Methods</h2>
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<P>
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C++ allows the use of abstract classes. Abstract classes cannot be used in programs
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(instantiated) directly; their only purpose is to serve as a base class from which
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programmers can derive other classes that can be used.
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</P>
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<P>
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An abstract class in C++ is defined as a class that has one or more 'pure virtual'
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methods. These can be identified in the C++ header files or C++ docs as methods set
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equal to 0, for example:
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</P>
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<TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%">
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<TR>
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<TD>
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<PRE CLASS="PROGRAMLISTING">
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virtual int somePureVirtualMethod (int a) = 0;
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</PRE>
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</TD>
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</TR>
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</TABLE>
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<P>
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To derive a useful class from the abstract class, the programmer has to write methods
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to overload each of the pure virtual methods. Following a suggestion on the mailing
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list, the docs attempt to flag all abstract classes and identify the pure virtual
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methods which must be overloaded in the derived class. Derived classes can be created
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in Python by writing Python methods to overload the pure virtual methods - no C++ code
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is required.
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</P>
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<TD WIDTH="33%" ALIGN="left" VALIGN="top"><A HREF="signal.html" ACCESSKEY="P">Prev</A></TD>
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<TD WIDTH="33%" ALIGN="left" VALIGN="top">Signals and Slots</TD>
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<TD WIDTH="34%" ALIGN="center" VALIGN="top"> </TD>
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<TD WIDTH="33%" ALIGN="right" VALIGN="top">Class Reference</TD>
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