+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% Name: variant.tex
+%% Purpose: wxVariant docs
+%% Author: wxWidgets Team
+%% Modified by:
+%% Created: 01/30/2005
+%% RCS-ID: $Id$
+%% Copyright: (c) wxWidgets Team
+%% License: wxWindows license
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
\section{\class{wxVariant}}\label{wxvariant}
The {\bf wxVariant} class represents a container for any type.
A variant's value can be changed at run time, possibly to a different type of value.
-As standard, wxVariant can store values of type bool, char, double, long, string,
-string list, time, date, void pointer, list of strings, and list of variants. However, an application can extend wxVariant's capabilities by deriving from the class \helpref{wxVariantData}{wxvariantdata} and using the wxVariantData form of the wxVariant constructor or assignment operator to assign this data to a variant. Actual values for user-defined types will need to be accessed via the wxVariantData object, unlike the case for basic data types where convenience functions such as GetLong can be used.
+As standard, wxVariant can store values of type bool, wxChar, double, long, string,
+string list, time, date, void pointer, list of strings, and list of variants.
+However, an application can extend wxVariant's capabilities by deriving from the
+class \helpref{wxVariantData}{wxvariantdata} and using the wxVariantData form of
+the wxVariant constructor or assignment operator to assign this data to a variant.
+Actual values for user-defined types will need to be accessed via the wxVariantData
+object, unlike the case for basic data types where convenience functions such as
+\helpref{GetLong}{wxvariantgetlong} can be used.
+
+Pointers to any \helpref{wxObject}{wxobject} derived class can also easily be stored
+in a wxVariant. wxVariant will then use wxWidgets' built-in RTTI system to set the
+type name (returned by \helpref{GetType}{wxvariantgettype}) and to perform
+type-safety checks at runtime.
This class is useful for reducing the programming for certain tasks, such as an editor
for different data types, or a remote procedure call protocol.
-An optional name member is associated with a wxVariant. This might be used, for example, in CORBA
-or OLE automation classes, where named parameters are required.
+An optional name member is associated with a wxVariant. This might be used, for example,
+in CORBA or OLE automation classes, where named parameters are required.
+
+Note that as of wxWidgets 2.7.1, wxVariant is reference counted. Additionally, the
+conveniance macros {\bf DECLARE\_VARIANT\_OBJECT} and {\bf IMPLEMENT\_VARIANT\_OBJECT}
+were added so that adding (limited) support for conversion to and from wxVariant
+can be very easily implemented without modifiying either wxVariant or the class
+to be stored by wxVariant. Since assignement operators cannot be declared outside
+the class, the shift left operators are used like this:
+
+\begin{verbatim}
+ // in the header file
+ DECLARE_VARIANT_OBJECT(MyClass)
+
+ // in the implementation file
+ IMPLMENT_VARIANT_OBJECT(MyClass)
+
+ // in the user code
+ wxVariant variant;
+ MyClass value;
+ variant << value;
+
+ // or
+ value << variant;
+\end{verbatim}
+
+For this to work, MyClass must derive from \helpref{wxObject}{wxobject}, implement
+the \helpref{wxWidgets RTTI system}{runtimeclassoverview}
+and support the assignment operator and equality operator for itself. Ideally, it
+should also be reference counted to make copying operations cheap and fast. This
+can be most easily implemented using the reference counting support offered by
+\helpref{wxObject}{wxobject} itself. By default, wxWidgets already implements
+the shift operator conversion for a few of its drawing related classes:
+
+\begin{verbatim}
+IMPLEMENT_VARIANT_OBJECT(wxColour)
+IMPLEMENT_VARIANT_OBJECT(wxImage)
+IMPLEMENT_VARIANT_OBJECT(wxIcon)
+IMPLEMENT_VARIANT_OBJECT(wxBitmap)
+\end{verbatim}
\wxheading{Derived from}
Copy constructor.
-\func{}{wxVariant}{\param{const char*}{ value}, \param{const wxString\& }{name = ``"}}
+\func{}{wxVariant}{\param{const wxChar*}{ value}, \param{const wxString\& }{name = ``"}}
\func{}{wxVariant}{\param{const wxString\&}{ value}, \param{const wxString\& }{name = ``"}}
Construction from a string value.
-\func{}{wxVariant}{\param{char}{ value}, \param{const wxString\& }{name = ``"}}
+\func{}{wxVariant}{\param{wxChar}{ value}, \param{const wxString\& }{name = ``"}}
Construction from a character value.
\func{}{wxVariant}{\param{wxDateTime\&}{ val}, \param{const wxString\& }{name = ``"}}
-Construction from a \helpref{wxDateTime}{wxdatetime}.
+Construction from a \helpref{wxDateTime}{wxdatetime}.
\func{}{wxVariant}{\param{wxArrayString\&}{ val}, \param{const wxString\& }{name = ``"}}
Destructor.
+Note that destructor is protected, so wxVariantData cannot usually
+be deleted. Instead, \helpref{DecRef}{wxvariantdatadecref} should be called.
+
\membersection{wxVariant::Append}\label{wxvariantappend}
Appends a value to the list.
+\membersection{wxVariant::Clear}\label{wxvariantclear}
+
+\func{void}{Clear}{\void}
+
+Makes the variant null by deleting the internal data and
+set the name to {\it wxEmptyString}.
+
\membersection{wxVariant::ClearList}\label{wxvariantclearlist}
\func{void}{ClearList}{\void}
\membersection{wxVariant::Convert}\label{wxvariantconvert}
-\constfunc{bool}{Convert}{long* value}
+\constfunc{bool}{Convert}{\param{long*}{ value}}
-\constfunc{bool}{Convert}{bool* value}
+\constfunc{bool}{Convert}{\param{bool*}{ value}}
-\constfunc{bool}{Convert}{double* value}
+\constfunc{bool}{Convert}{\param{double*}{ value}}
-\constfunc{bool}{Convert}{wxString* value}
+\constfunc{bool}{Convert}{\param{wxString*}{ value}}
-\constfunc{bool}{Convert}{char* value}
+\constfunc{bool}{Convert}{\param{wxChar*}{ value}}
-\constfunc{bool}{Convert}{wxDateTime* value}
+\constfunc{bool}{Convert}{\param{wxDateTime*}{ value}}
Retrieves and converts the value of this variant to the type that {\it value} is.
\membersection{wxVariant::GetCount}\label{wxvariantgetcount}
-\constfunc{int}{GetCount}{\void}
+\constfunc{size\_t}{GetCount}{\void}
Returns the number of elements in the list.
\membersection{wxVariant::Delete}\label{wxvariantdelete}
-\func{bool}{Delete}{\param{int }{item}}
+\func{bool}{Delete}{\param{size\_t }{item}}
Deletes the zero-based {\it item} from the list.
\membersection{wxVariant::GetChar}\label{wxvariantgetchar}
-\constfunc{char}{GetChar}{\void}
+\constfunc{wxChar}{GetChar}{\void}
Returns the character value.
\constfunc{wxVariantData*}{GetData}{\void}
-Returns a pointer to the internal variant data.
+Returns a pointer to the internal variant data. To take ownership
+of this data, you must call its \helpref{IncRef}{wxvariantdataincref}
+method. When you stop using it, \helpref{DecRef}{wxvariantdatadecref}
+must be likewise called.
\membersection{wxVariant::GetDateTime}\label{wxvariantgetdatetime}
\membersection{wxVariant::GetWxObjectPtr}\label{wxvariantgetwxobjectptr}
-\constfunc{void*}{GetWxObjectPtr}{\void}
+\constfunc{wxObject*}{GetWxObjectPtr}{\void}
Gets the wxObject pointer value.
\func{void}{operator $=$}{\param{const wxString\& }{value}}
-\func{void}{operator $=$}{\param{const char* }{value}}
+\func{void}{operator $=$}{\param{const wxChar* }{value}}
-\func{void}{operator $=$}{\param{char }{value}}
+\func{void}{operator $=$}{\param{wxChar }{value}}
\func{void}{operator $=$}{\param{const long }{value}}
\func{void}{operator $=$}{\param{void* }{value}}
+\func{void}{operator $=$}{\param{wxObject* }{value}}
+
\func{void}{operator $=$}{\param{const wxList\& }{value}}
\func{void}{operator $=$}{\param{const wxDateTime\& }{value}}
\constfunc{bool}{operator $==$}{\param{const wxString\& }{value}}
-\constfunc{bool}{operator $==$}{\param{const char* }{value}}
+\constfunc{bool}{operator $==$}{\param{const wxChar* }{value}}
-\constfunc{bool}{operator $==$}{\param{char }{value}}
+\constfunc{bool}{operator $==$}{\param{wxChar }{value}}
\constfunc{bool}{operator $==$}{\param{const long }{value}}
\constfunc{bool}{operator $==$}{\param{void* }{value}}
+\constfunc{bool}{operator $==$}{\param{wxObject* }{value}}
+
\constfunc{bool}{operator $==$}{\param{const wxList\& }{value}}
\constfunc{bool}{operator $==$}{\param{const wxArrayString\& }{value}}
\constfunc{bool}{operator $!=$}{\param{const wxString\& }{value}}
-\constfunc{bool}{operator $!=$}{\param{const char* }{value}}
+\constfunc{bool}{operator $!=$}{\param{const wxChar* }{value}}
-\constfunc{bool}{operator $!=$}{\param{char }{value}}
+\constfunc{bool}{operator $!=$}{\param{wxChar }{value}}
\constfunc{bool}{operator $!=$}{\param{const long }{value}}
\constfunc{bool}{operator $!=$}{\param{void* }{value}}
+\constfunc{bool}{operator $!=$}{\param{wxObject* }{value}}
+
\constfunc{bool}{operator $!=$}{\param{const wxList\& }{value}}
\constfunc{bool}{operator $!=$}{\param{const wxArrayString\& }{value}}
Returns a reference to the value at {\it idx} (zero-based). This can be used
to change the value at this index.
-\membersection{wxVariant::operator char}\label{wxvariantchar}
+\membersection{wxVariant::operator wxChar}\label{wxvariantchar}
-\constfunc{char}{operator char}{\void}
+\constfunc{char}{operator wxChar}{\void}
-Operator for implicit conversion to a char, using \helpref{wxVariant::GetChar}{wxvariantgetchar}.
+Operator for implicit conversion to a wxChar, using \helpref{wxVariant::GetChar}{wxvariantgetchar}.
\membersection{wxVariant::operator double}\label{wxvariantdouble}
The {\bf wxVariantData} is used to implement a new type for wxVariant. Derive from wxVariantData,
and override the pure virtual functions.
+wxVariantData is reference counted, but you don't normally have to care about this, as
+wxVariant manages the count automatically. However, incase your application needs to take
+ownership of wxVariantData, be aware that the object is created with reference count of 1,
+and passing it to wxVariant will not increase this. In other words, \helpref{IncRef}{wxvariantdataincref}
+needs to be called only if you both take ownership of wxVariantData and pass it to a wxVariant.
+Also note that the destructor is protected, so you can never explicitly delete a wxVariantData
+instance. Instead, \helpref{DecRef}{wxvariantdatadecref} will delete the object automatically
+when the reference count reaches zero.
+
\wxheading{Derived from}
\helpref{wxObject}{wxobject}
Default constructor.
-\membersection{wxVariantData::Copy}\label{wxvariantdatacopy}
+\membersection{wxVariantData::DecRef}\label{wxvariantdatadecref}
+
+\func{void}{DecRef}{\void}
-\func{void}{Copy}{\param{wxVariantData\&}{ data}}
+Decreases reference count. If the count reaches zero, the object is
+automatically deleted.
-Copy the data from `this' object to {\it data}.
+Note that destructor of wxVariantData is protected, so delete
+cannot be used as normal. Instead, DecRef should be called.
\membersection{wxVariantData::Eq}\label{wxvariantdataeq}
If the data is a wxObject returns a pointer to the objects wxClassInfo structure, if
the data isn't a wxObject the method returns NULL.
+\membersection{wxVariantData::IncRef}\label{wxvariantdataincref}
+
+\func{void}{IncRef}{\void}
+
+Increases reference count. Note that initially wxVariantData has reference count of 1.
+
\membersection{wxVariantData::Read}\label{wxvariantdataread}
\func{bool}{Read}{\param{ostream\&}{ stream}}
This macro returns the data stored in {\it variant} cast to the type {\it classname *} if
the data is of this type (the check is done during the run-time) or
-{\tt NULL} otherwise.
+{\tt NULL} otherwise.
\wxheading{See also}
projects / wxWidgets.git / blobdiff