    wxVariantThe 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, 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 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. Pointers to any 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 GetType) 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. Note that as of wxWidgets 2.7.1, wxVariant is reference counted. Additionally, the convenience macros DECLARE_VARIANT_OBJECT and IMPLEMENT_VARIANT_OBJECT were added so that adding (limited) support for conversion to and from wxVariant can be very easily implemented without modifying either wxVariant or the class to be stored by wxVariant. Since assignment operators cannot be declared outside the class, the shift left operators are used like this:
// in the header file
DECLARE_VARIANT_OBJECT(MyClass)
// in the implementation file
IMPLEMENT_VARIANT_OBJECT(MyClass)
// in the user code
wxVariant variant;
MyClass value;
variant << value;
// or
value << variant;
For this to work, MyClass must derive from wxObject, implement
the wxWidgets RTTI system
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
wxObject itself. By default, wxWidgets already implements
the shift operator conversion for a few of its drawing related classes:
IMPLEMENT_VARIANT_OBJECT(wxColour) IMPLEMENT_VARIANT_OBJECT(wxImage) IMPLEMENT_VARIANT_OBJECT(wxIcon) IMPLEMENT_VARIANT_OBJECT(wxBitmap)Derived from Include files <wx/variant.h> See also Members
wxVariant::wxVariant
wxVariant::wxVariantwxVariant() Default constructor. wxVariant(const wxVariant& variant) Copy constructor, uses reference counting. wxVariant(const wxChar* value, const wxString& name = "") wxVariant(const wxString& value, const wxString& name = "") Construction from a string value. wxVariant(wxChar value, const wxString& name = "") Construction from a character value. wxVariant(long value, 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). wxVariant(bool value, const wxString& name = "") Construction from a boolean value. wxVariant(double value, const wxString& name = "") Construction from a double-precision floating point value. wxVariant(const wxList& value, const wxString& name = "") Construction from a list of wxVariant objects. This constructor copies value, the application is still responsible for deleting value and its contents. wxVariant(void* value, const wxString& name = "") Construction from a void pointer. wxVariant(wxObject* value, const wxString& name = "") Construction from a wxObject pointer. wxVariant(wxVariantData* data, const wxString& name = "") Construction from user-defined data. The variant holds onto the data pointer. wxVariant(wxDateTime& val, const wxString& name = "") Construction from a wxDateTime. wxVariant(wxArrayString& val, const wxString& name = "") Construction from an array of strings. This constructor copies value and its contents. wxVariant(DATE_STRUCT* val, const wxString& name = "") Construction from a odbc date value. Represented internally by a wxDateTime value. wxVariant(TIME_STRUCT* val, const wxString& name = "") Construction from a odbc time value. Represented internally by a wxDateTime value. wxVariant(TIMESTAMP_STRUCT* val, const wxString& name = "") Construction from a odbc timestamp value. Represented internally by a wxDateTime value.
wxVariant::~wxVariant~wxVariant() Destructor. Note that destructor is protected, so wxVariantData cannot usually be deleted. Instead, DecRef should be called. See reference-counted object destruction for more info.
wxVariant::Appendvoid Append(const wxVariant& value) Appends a value to the list.
wxVariant::Clearvoid Clear() Makes the variant null by deleting the internal data and set the name to wxEmptyString.
wxVariant::ClearListvoid ClearList() Deletes the contents of the list.
wxVariant::Convertbool Convert(long* value) const bool Convert(bool* value) const bool Convert(double* value) const bool Convert(wxString* value) const bool Convert(wxChar* value) const bool Convert(wxDateTime* value) const Retrieves and converts the value of this variant to the type that value is.
wxVariant::GetCountsize_t GetCount() const Returns the number of elements in the list.
wxVariant::Deletebool Delete(size_t item) Deletes the zero-based item from the list.
wxVariant::GetArrayStringwxArrayString GetArrayString() const Returns the string array value.
wxVariant::GetBoolbool GetBool() const Returns the boolean value.
wxVariant::GetCharwxChar GetChar() const Returns the character value.
wxVariant::GetDatawxVariantData* GetData() const Returns a pointer to the internal variant data. To take ownership of this data, you must call its IncRef method. When you stop using it, DecRef must be likewise called.
wxVariant::GetDateTimewxDateTime GetDateTime() const Returns the date value.
wxVariant::GetDoubledouble GetDouble() const Returns the floating point value.
wxVariant::GetLonglong GetLong() const Returns the integer value.
wxVariant::GetNameconst wxString& GetName() const Returns a constant reference to the variant name.
wxVariant::GetStringwxString GetString() const Gets the string value.
wxVariant::GetTypewxString GetType() const 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).
wxVariant::GetVoidPtrvoid* GetVoidPtr() const Gets the void pointer value.
wxVariant::GetWxObjectPtrwxObject* GetWxObjectPtr() const Gets the wxObject pointer value.
wxVariant::Insertvoid Insert(const wxVariant& value) Inserts a value at the front of the list.
wxVariant::IsNullbool IsNull() const Returns true if there is no data associated with this variant, false if there is data.
wxVariant::IsTypebool IsType(const wxString& type) const Returns true if type matches the type of the variant, false otherwise.
wxVariant::IsValueKindOfbool IsValueKindOf(const wxClassInfo* type type) const Returns true if the data is derived from the class described by type, false otherwise.
wxVariant::MakeNullvoid MakeNull() Makes the variant null by deleting the internal data.
wxVariant::MakeStringwxString MakeString() const Makes a string representation of the variant value (for any type).
wxVariant::Memberbool Member(const wxVariant& value) const Returns true if value matches an element in the list.
wxVariant::NullListvoid NullList() 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.
wxVariant::SetDatavoid SetData(wxVariantData* data) Sets the internal variant data, deleting the existing data if there is any.
wxVariant::operator =void operator =(const wxVariant& value) void operator =(wxVariantData* value) void operator =(const wxString& value) void operator =(const wxChar* value) void operator =(wxChar value) void operator =(const long value) void operator =(const bool value) void operator =(const double value) void operator =(void* value) void operator =(wxObject* value) void operator =(const wxList& value) void operator =(const wxDateTime& value) void operator =(const wxArrayString& value) void operator =(const DATE_STRUCT* value) void operator =(const TIME_STRUCT* value) void operator =(const TIMESTAMP_STRUCT* value) Assignment operators, using reference counting when possible.
wxVariant::operator ==bool operator ==(const wxVariant& value) const bool operator ==(const wxString& value) const bool operator ==(const wxChar* value) const bool operator ==(wxChar value) const bool operator ==(const long value) const bool operator ==(const bool value) const bool operator ==(const double value) const bool operator ==(void* value) const bool operator ==(wxObject* value) const bool operator ==(const wxList& value) const bool operator ==(const wxArrayString& value) const bool operator ==(const wxDateTime& value) const Equality test operators.
wxVariant::operator !=bool operator !=(const wxVariant& value) const bool operator !=(const wxString& value) const bool operator !=(const wxChar* value) const bool operator !=(wxChar value) const bool operator !=(const long value) const bool operator !=(const bool value) const bool operator !=(const double value) const bool operator !=(void* value) const bool operator !=(wxObject* value) const bool operator !=(const wxList& value) const bool operator !=(const wxArrayString& value) const bool operator !=(const wxDateTime& value) const Inequality test operators.
wxVariant::operator []wxVariant operator [](size_t idx) const Returns the value at idx (zero-based). wxVariant& operator [](size_t idx) Returns a reference to the value at idx (zero-based). This can be used to change the value at this index.
wxVariant::operator wxCharchar operator wxChar() const Operator for implicit conversion to a wxChar, using wxVariant::GetChar.
wxVariant::operator doubledouble operator double() const Operator for implicit conversion to a double, using wxVariant::GetDouble. long operator long() const Operator for implicit conversion to a long, using wxVariant::GetLong.
wxVariant::operator wxStringwxString operator wxString() const Operator for implicit conversion to a string, using wxVariant::MakeString.
wxVariant::operator void*void* operator void*() const Operator for implicit conversion to a pointer to a void, using wxVariant::GetVoidPtr.
wxVariant::operator wxDateTimevoid* operator wxDateTime() const Operator for implicit conversion to a pointer to a wxDateTime, using wxVariant::GetDateTime.
|