Fixes the problem with VARCHAR fields not allowing the stored string to ever be lengt...

[wxWidgets.git] / docs / latex / wx / variant.tex

\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.

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.

wxVariant is similar to wxExpr and also to wxPropertyValue. However, wxExpr is efficiency-optimized for
a restricted range of data types, whereas wxVariant is less efficient but more extensible.
wxPropertyValue may be replaced by wxVariant eventually.

\wxheading{Derived from}

\helpref{wxObject}{wxobject}

\wxheading{Include files}

<wx/variant.h>

\wxheading{See also}

\helpref{wxVariantData}{wxvariantdata}

\latexignore{\rtfignore{\wxheading{Members}}}

\membersection{wxVariant::wxVariant}\label{wxvariantctor}

\func{}{wxVariant}{\void}

Default constructor.

\func{}{wxVariant}{\param{const wxVariant\& }{variant}}

Copy constructor.

\func{}{wxVariant}{\param{const char*}{ 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 = ``"}}

Construction from a character value.

\func{}{wxVariant}{\param{long}{ value}, \param{const wxString\& }{name = ``"}}

Construction from an integer value. You may need to cast to (long) to
avoid confusion with other constructors (such as the bool constructor).

\func{}{wxVariant}{\param{bool}{ value}, \param{const wxString\& }{name = ``"}}

Construction from a boolean value.

\func{}{wxVariant}{\param{double}{ value}, \param{const wxString\& }{name = ``"}}

Construction from a double-precision floating point value.

\func{}{wxVariant}{\param{const wxList\&}{ value}, \param{const wxString\& }{name = ``"}}

Construction from a list of wxVariant objects. This constructor
copies {\it value}, the application is still responsible for
deleting {\it value} and its contents.

\func{}{wxVariant}{\param{const wxStringList\&}{ value}, \param{const wxString\& }{name = ``"}}

Construction from a list of strings. This constructor
copies {\it value}, the application is still responsible for
deleting {\it value} and its contents.

%Note: this constructor is currently disabled because it causes a C++ ambiguity.

\func{}{wxVariant}{\param{const wxTime\&}{ value}, \param{const wxString\& }{name = ``"}}

Construction from a time.

\func{}{wxVariant}{\param{const wxDate\&}{ value}, \param{const wxString\& }{name = ``"}}

Construction from a date.

\func{}{wxVariant}{\param{void*}{ value}, \param{const wxString\& }{name = ``"}}

Construction from a void pointer.

\func{}{wxVariant}{\param{wxVariantData*}{ data}, \param{const wxString\& }{name = ``"}}

Construction from user-defined data. The variant holds on to the {\it data} pointer.

\membersection{wxVariant::\destruct{wxVariant}}\label{wxvariantdtor}

\func{}{\destruct{wxVariant}}{\void}

Destructor.

\membersection{wxVariant::Append}\label{wxvariantappend}

\func{void}{Append}{\param{const wxVariant\&}{ value}}

Appends a value to the list.

\membersection{wxVariant::ClearList}\label{wxvariantclearlist}

\func{void}{ClearList}{\void}

Deletes the contents of the list.

\membersection{wxVariant::GetCount}\label{wxvariantgetcount}

\constfunc{int}{GetCount}{\void}

Returns the number of elements in the list.

\membersection{wxVariant::Delete}\label{wxvariantdelete}

\func{bool}{Delete}{\param{int }{item}}

Deletes the zero-based {\it item} from the list.

\membersection{wxVariant::GetBool}\label{wxvariantgetbool}

\constfunc{bool}{GetBool}{\void}

Returns the boolean value.

\membersection{wxVariant::GetChar}\label{wxvariantgetchar}

\constfunc{char}{GetChar}{\void}

Returns the character value.

\membersection{wxVariant::GetData}\label{wxvariantgetdata}

\constfunc{wxVariantData*}{GetData}{\void}

Returns a pointer to the internal variant data.

\membersection{wxVariant::GetDate}\label{wxvariantgetdate}

\constfunc{wxDate}{GetDate}{\void}

Gets the date value.

\membersection{wxVariant::GetDouble}\label{wxvariantgetdouble}

\constfunc{double}{GetDouble}{\void}

Returns the floating point value.

\membersection{wxVariant::GetLong}\label{wxvariantgetlong}

\constfunc{long}{GetLong}{\void}

Returns the integer value.

\membersection{wxVariant::GetName}\label{wxvariantgetname}

\constfunc{const wxString\&}{GetName}{\void}

Returns a constant reference to the variant name.

\membersection{wxVariant::GetString}\label{wxvariantgetstring}

\constfunc{wxString}{GetString}{\void}

Gets the string value.

\membersection{wxVariant::GetTime}\label{wxvariantgettime}

\constfunc{wxTime}{GetTime}{\void}

Gets the time value.

\membersection{wxVariant::GetType}\label{wxvariantgettype}

\constfunc{wxString}{GetType}{\void}

Returns the value type as a string. The built-in types are: bool, char, date, double, list, long, string, stringlist, time, void*.

If the variant is null, the value type returned is the string ``null" (not the empty string).

\membersection{wxVariant::GetVoidPtr}\label{wxvariantgetvoidptr}

\constfunc{void*}{GetVoidPtr}{\void}

Gets the void pointer value.

\membersection{wxVariant::Insert}\label{wxvariantinsert}

\func{void}{Insert}{\param{const wxVariant\&}{ value}}

Inserts a value at the front of the list.

\membersection{wxVariant::IsNull}\label{wxvariantisnull}

\constfunc{bool}{IsNull}{\void}

Returns TRUE if there is no data associated with this variant, FALSE if there is data.

\membersection{wxVariant::IsType}\label{wxvariantistype}

\constfunc{bool}{IsType}{\param{const wxString\&}{ type}}

Returns TRUE if {\it type} matches the type of the variant, FALSE otherwise.

\membersection{wxVariant::MakeNull}\label{wxvariantmakenull}

\func{void}{MakeNull}{\void}

Makes the variant null by deleting the internal data.

\membersection{wxVariant::MakeString}\label{wxvariantmakestring}

\constfunc{wxString}{MakeString}{\void}

Makes a string representation of the variant value (for any type).

\membersection{wxVariant::Member}\label{wxvariantmember}

\constfunc{bool}{Member}{\param{const wxVariant\&}{ value}}

Returns TRUE if {\it value} matches an element in the list.

\membersection{wxVariant::NullList}\label{wxvariantnulllist}

\func{void}{NullList}{\void}

Makes an empty list. This differs from a null variant which has no data; a null list
is of type list, but the number of elements in the list is zero.

\membersection{wxVariant::SetData}\label{wxvariantsetdata}

\func{void}{SetData}{\param{wxVariantData*}{ data}}

Sets the internal variant data, deleting the existing data if there is any.

\membersection{wxVariant::operator $=$}\label{wxvariantassignment}

\func{void}{operator $=$}{\param{const wxVariant\& }{value}}

\func{void}{operator $=$}{\param{wxVariantData* }{value}}

\func{void}{operator $=$}{\param{const wxString\& }{value}}

\func{void}{operator $=$}{\param{const char* }{value}}

\func{void}{operator $=$}{\param{char }{value}}

\func{void}{operator $=$}{\param{const long }{value}}

\func{void}{operator $=$}{\param{const bool }{value}}

\func{void}{operator $=$}{\param{const double }{value}}

\func{void}{operator $=$}{\param{const wxDate\& }{value}}

\func{void}{operator $=$}{\param{const wxTime\& }{value}}

\func{void}{operator $=$}{\param{void* }{value}}

\func{void}{operator $=$}{\param{const wxList\& }{value}}

\func{void}{operator $=$}{\param{const wxStringList\& }{value}}

Assignment operators.

\membersection{wxVariant::operator $==$}\label{wxvarianteq}

\func{bool}{operator $==$}{\param{const wxVariant\& }{value}}

\func{bool}{operator $==$}{\param{const wxString\& }{value}}

\func{bool}{operator $==$}{\param{const char* }{value}}

\func{bool}{operator $==$}{\param{char }{value}}

\func{bool}{operator $==$}{\param{const long }{value}}

\func{bool}{operator $==$}{\param{const bool }{value}}

\func{bool}{operator $==$}{\param{const double }{value}}

\func{bool}{operator $==$}{\param{const wxDate\& }{value}}

\func{bool}{operator $==$}{\param{const wxTime\& }{value}}

\func{bool}{operator $==$}{\param{void* }{value}}

\func{bool}{operator $==$}{\param{const wxList\& }{value}}

\func{bool}{operator $==$}{\param{const wxStringList\& }{value}}

Equality test operators.

\membersection{wxVariant::operator $!=$}\label{wxvariantneq}

\func{bool}{operator $!=$}{\param{const wxVariant\& }{value}}

\func{bool}{operator $!=$}{\param{const wxString\& }{value}}

\func{bool}{operator $!=$}{\param{const char* }{value}}

\func{bool}{operator $!=$}{\param{char }{value}}

\func{bool}{operator $!=$}{\param{const long }{value}}

\func{bool}{operator $!=$}{\param{const bool }{value}}

\func{bool}{operator $!=$}{\param{const double }{value}}

\func{bool}{operator $!=$}{\param{const wxDate\& }{value}}

\func{bool}{operator $!=$}{\param{const wxTime\& }{value}}

\func{bool}{operator $!=$}{\param{void* }{value}}

\func{bool}{operator $!=$}{\param{const wxList\& }{value}}

\func{bool}{operator $!=$}{\param{const wxStringList\& }{value}}

Inequality test operators.

\membersection{wxVariant::operator $[]$}\label{wxvariantarray}

\constfunc{wxVariant}{operator $[]$}{\param{size\_t }{idx}}

Returns the value at {\it idx} (zero-based).

\func{wxVariant\&}{operator $[]$}{\param{size\_t }{idx}}

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}

\constfunc{char}{operator char}{\void}

Operator for implicit conversion to a char, using \helpref{wxVariant::GetChar}{wxvariantgetchar}.

\membersection{wxVariant::operator double}\label{wxvariantdouble}

\constfunc{double}{operator double}{\void}

Operator for implicit conversion to a double, using \helpref{wxVariant::GetDouble}{wxvariantgetdouble}.

\constfunc{long}{operator long}{\void}

Operator for implicit conversion to a long, using \helpref{wxVariant::GetLong}{wxvariantgetlong}.

\membersection{wxVariant::operator wxDate}\label{wxvariantwxdate}

\constfunc{wxDate}{operator wxDate}{\void}

Operator for implicit conversion to a wxDate, using \helpref{wxVariant::GetDate}{wxvariantgetdate}.

\membersection{wxVariant::operator wxString}\label{wxvariantwxstring}

\constfunc{wxString}{operator wxString}{\void}

Operator for implicit conversion to a string, using \helpref{wxVariant::MakeString}{wxvariantmakestring}.

\membersection{wxVariant::operator wxTime}\label{wxvariantwxtime}

\constfunc{wxTime}{operator wxTime}{\void}

Operator for implicit conversion to a wxTime, using \helpref{wxVariant::GetTime}{wxvariantgettime}.

\membersection{wxVariant::operator void*}\label{wxvariantvoid}

\constfunc{void*}{operator void*}{\void}

Operator for implicit conversion to a pointer to a void, using \helpref{wxVariant::GetVoidPtr}{wxvariantgetvoidptr}.

\section{\class{wxVariantData}}\label{wxvariantdata}

The {\bf wxVariantData} is used to implement a new type for wxVariant. Derive from wxVariantData,
and override the pure virtual functions.

\wxheading{Derived from}

\helpref{wxObject}{wxobject}

\wxheading{Include files}

<wx/variant.h>

\wxheading{See also}

\helpref{wxVariant}{wxvariant}

\latexignore{\rtfignore{\wxheading{Members}}}

\membersection{wxVariantData::wxVariantData}\label{wxvariantdatactor}

\func{}{wxVariantData}{\void}

Default constructor.

\membersection{wxVariantData::Copy}\label{wxvariantdatacopy}

\func{void}{Copy}{\param{wxVariantData\&}{ data}}

Copy the data from `this' object to {\it data}.

\membersection{wxVariantData::Eq}\label{wxvariantdataeq}

\constfunc{bool}{Eq}{\param{wxVariantData\&}{ data}}

Returns TRUE if this object is equal to {\it data}.

\membersection{wxVariantData::GetType}\label{wxvariantdatagettype}

\constfunc{wxString}{GetType}{\void}

Returns the string type of the data.

\membersection{wxVariantData::Read}\label{wxvariantdataread}

\func{bool}{Read}{\param{ostream\&}{ stream}}

\func{bool}{Read}{\param{wxString\&}{ string}}

Reads the data from {\it stream} or {\it string}.

\membersection{wxVariantData::Write}\label{wxvariantdatawrite}

\constfunc{bool}{Write}{\param{ostream\&}{ stream}}

\constfunc{bool}{Write}{\param{wxString\&}{ string}}

Writes the data to {\it stream} or {\it string}.