X-Git-Url: https://git.saurik.com/wxWidgets.git/blobdiff_plain/a660d684eda27638bca0384b2058911a31c8e845..020e2e811ea02751c25de488b74d947115ca7b8f:/docs/latex/wx/truntime.tex diff --git a/docs/latex/wx/truntime.tex b/docs/latex/wx/truntime.tex index 2d1da9c021..04ee1e02a7 100644 --- a/docs/latex/wx/truntime.tex +++ b/docs/latex/wx/truntime.tex @@ -1,19 +1,34 @@ -\section{Run time class information overview}\label{runtimeclassoverview} +\section{Runtime class information (aka RTTI) overview}\label{runtimeclassoverview} Classes: \helpref{wxObject}{wxobject}, \helpref{wxClassInfo}{wxclassinfo}. -One of the failings of C++ is that no run-time information is provided +One of the failings of C++ used to be that no run-time information was provided about a class and its position in the inheritance hierarchy. -Another is that instances of a class cannot be created just by knowing the name of a class, -which makes facilities such as persistent storage hard to implement. +Another, which still persists, is that instances of a class cannot be created +just by knowing the name of a class, which makes facilities such as persistent +storage hard to implement. Most C++ GUI frameworks overcome these limitations by means of a set of -macros and functions and wxWindows (from version 1.62) is no exception. -Each class that you wish to be known the type system should have +macros and functions and wxWidgets is no exception. As it originated before the +addition of RTTI to the C++ standard and as support for it is still missing from +some (albeit old) compilers, wxWidgets doesn't (yet) use it, but provides its +own macro-based RTTI system. + +In the future, the standard C++ RTTI will be used though and you're encouraged +to use whenever possible the \helpref{wxDynamicCast()}{wxdynamiccast} macro which, +for the implementations that support it, is defined just as dynamic\_cast<> and +uses wxWidgets RTTI for all the others. This macro is limited to wxWidgets +classes only and only works with pointers (unlike the real dynamic\_cast<> which +also accepts references). + +Each class that you wish to be known to the type system should have a macro such as DECLARE\_DYNAMIC\_CLASS just inside the class declaration. The macro IMPLEMENT\_DYNAMIC\_CLASS should be in the implementation file. +Note that these are entirely optional; use them if you wish to check object +types, or create instances of classes using the class name. However, +it is good to get into the habit of adding these macros for all classes. -Variations on these \helpref{macros}{macros} are used for multiple inheritance, and abstract +Variations on these \helpref{macros}{rttimacros} are used for multiple inheritance, and abstract classes that cannot be instantiated dynamically or otherwise. DECLARE\_DYNAMIC\_CLASS inserts a static wxClassInfo declaration into the @@ -28,18 +43,18 @@ dynamic object of the class in question. A pointer to this function is stored in wxClassInfo, and is used when an object should be created dynamically. -wxObject::IsKindOf uses the linked list of wxClassInfo. It takes -a wxClassInfo argument, so use CLASSINFO(className) to return an -appropriate wxClassInfo pointer to use in this function. +\helpref{wxObject::IsKindOf}{wxobjectiskindof} uses the linked list of +wxClassInfo. It takes a wxClassInfo argument, so use CLASSINFO(className) +to return an appropriate wxClassInfo pointer to use in this function. The function \helpref{wxCreateDynamicObject}{wxcreatedynamicobject} can be used to construct a new object of a given type, by supplying a string name. If you have a pointer to the wxClassInfo object instead, then you -can simply call wxClassInfo::CreateObject. +can simply call \helpref{wxClassInfo::CreateObject}{wxclassinfocreateobject}. \subsection{wxClassInfo}\label{wxclassinfooverview} -\overview{Run time class information overview}{runtimeclassoverview} +\overview{Runtime class information (aka RTTI) overview}{runtimeclassoverview} Class: \helpref{wxClassInfo}{wxclassinfo} @@ -63,28 +78,29 @@ You can get the wxClassInfo for an object using wxObject::GetClassInfo. See also \helpref{wxObject}{wxobject} and \helpref{wxCreateDynamicObject}{wxcreatedynamicobject}. -\subsection{Example} +\subsection{Example}\label{runtimeclassinformationexample} -In a header file wx\_frame.h: +In a header file frame.h: \begin{verbatim} -class wxFrame: public wxWindow +class wxFrame : public wxWindow { - DECLARE_DYNAMIC_CLASS(wxFrame) +DECLARE_DYNAMIC_CLASS(wxFrame) - private: - char *frameTitle; - public: - ... +private: + wxString m_title; + +public: + ... }; \end{verbatim} -In a C++ file wx\_frame.cc: +In a C++ file frame.cpp: \begin{verbatim} IMPLEMENT_DYNAMIC_CLASS(wxFrame, wxWindow) -wxFrame::wxFrame(void) +wxFrame::wxFrame() { ... }