Wt::any_traits< Type > Struct Template Reference

A traits class for a type stored in a cpp17::any. More...

#include <WAny.h>

Static Public Member Functions
static WString	asString (const Type &value, const WString &format)
	Converts a value to a string. More...
static double	asNumber (const Type &v)
	Converts a value to a number. More...
static int	compare (const Type &v1, const Type &v2)
	Compares two values. More...

Detailed Description

template<typename Type>
struct Wt::any_traits< Type >

A traits class for a type stored in a cpp17::any.

The traits are used by Wt's view classes (such as Wt::WTableView Wt::WTreeView, Wt::Chart::WCartesianChart) to deal with values in a Wt::WAbstractItemModel:

• conversion to a string by Wt::asString()
• conversion to a number by Wt::asNumber()
• sorting by Wt::WSortFilterProxyModel or WStandardItemModel.

This traits class provides a default implementation for supporting values value of a custom type Type in Wt's MVC system, which relies on:

• serializing to a stream (std::ostream << value) for converting the value to a string.
• lexical interpretation as a number for converting the value to a number, using std::stod()
• sorting using operator== and operator<

You can specialize these traits if you need to customize one or more of these operations.

Member Function Documentation

template<typename Type >

double Wt::any_traits< Type >::asNumber ( const Type &  v )

static

Converts a value to a number.

The default implementation uses std::stod() on the string value

template<typename Type >

WString Wt::any_traits< Type >::asString ( const Type &  value, const WString &  format  )

static

Converts a value to a string.

The default implementation uses std::ostream<< operator for the value.

template<typename Type >

int Wt::any_traits< Type >::compare ( const Type &  v1, const Type &  v2  )

static

Compares two values.

The default implementation uses operator== and operator<.