Arg

#include <Ultralight/js/Value.h>

Overview

An argument passed to a bound function.

An Arg is only valid during the callback that received it (it adds no reference, so reading it is cheap). Call ToValue() to keep the argument after the callback returns.

An Arg has To(), Maybe(), and Or(). Other conversions need a Value first (eg, arg.ToValue().ToNumber()).

See also

CallInfo::arg()

Public Member Functions
	Arg (ULJSValue borrowed)
	Wrap a borrowed handle.
bool	IsEmpty () const
	Whether or not the argument is absent (the call passed fewer arguments than the index given to CallInfo::arg()).
Type	type () const
	Get the argument's type (Type::Invalid if the argument is absent).
template<typename T>
Result< T >	To () const
	Convert to a C++ type (see Value::To()).
template<typename T>
std::optional< T >	Maybe () const
	Convert to a C++ type like To() but without the failure reason.
template<typename T>
T	Or (T fallback) const
	Convert to a C++ type like To() but with a fallback.
std::string	Or (const char *fallback) const
	Convert to a std::string like To() but with a string-literal fallback.
Value	ToValue () const
	Get a Value that keeps the argument after the callback returns.
ULJSValue	raw () const
	Get the C API handle.

Constructor & Destructor Documentation

Arg()

Arg ( ULJSValue borrowed )

inlineexplicit

Wrap a borrowed handle.

Parameters

borrowed

The handle (valid only during the callback).

Note

You normally get an Arg from CallInfo::arg() instead of creating one.

Member Function Documentation

IsEmpty()

bool IsEmpty ( ) const

inline

Whether or not the argument is absent (the call passed fewer arguments than the index given to CallInfo::arg()).

Note

An absent argument converts only to an optional type (as an empty optional). Any other To() fails with a TypeError, and ToValue() returns an empty Value.

Maybe()

template<typename T>

std::optional< T > Maybe ( ) const

nodiscard

Convert to a C++ type like To() but without the failure reason.

Returns

Returns the converted value or nullopt on any failure.

Or() [1/2]

std::string Or ( const char * fallback ) const

nodiscard

Convert to a std::string like To() but with a string-literal fallback.

Parameters

fallback

The text to return if the conversion fails.

Returns

Returns the converted string or fallback on any failure.

Or() [2/2]

template<typename T>

T Or ( T fallback ) const

nodiscard

Convert to a C++ type like To() but with a fallback.

Parameters

fallback

The value to return if the conversion fails.

Returns

Returns the converted value or fallback on any failure.

raw()

ULJSValue raw ( ) const

inline

Get the C API handle.

Returns

Returns the handle (valid only during the callback).

To()

template<typename T>

Result< T > To ( ) const

nodiscard

Convert to a C++ type (see Value::To()).

Returns

Returns the converted value and fails the same way as Value::To().

Note

Requires <Ultralight/js/TypeTraits.h> (or any header that includes it).

ToValue()

Value ToValue ( ) const

inline

Get a Value that keeps the argument after the callback returns.

Returns

Returns the new Value.

type()

Type type ( ) const

inline

Get the argument's type (Type::Invalid if the argument is absent).

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The documentation for this class was generated from the following file:

• Ultralight/js/Value.h