Value::Ref

#include <Ultralight/js/Value.h>

Overview

A reference to a property of a Value (returned by Value::operator[]).

Reading a Ref gives you the property's value, assigning to it sets the property, and calling it calls the property as a method of the object. Refs chain (obj["a"]["b"] = 1).

Use a Ref within one expression. To keep a property's value, read it into a Value.

Note

A Ref has To(), Maybe(), and Or(). For the other conversions, read the property first (eg, obj["volume"].Get().ToNumber()).

Public Member Functions
Value	Get () const
	Read the property.
	operator Value () const
	Read the property (the same as Get()).
template<typename T>
Ref &	operator= (T &&value)
	Set the property to value (converted through js::TypeTraits).
Ref	operator[] (const char *name) const
	Read this property and access a property of its value.
template<typename I> requires (std::is_integral_v<I> && !std::is_same_v<I, bool>)
Ref	operator[] (I index) const
template<typename R = Value, typename... A>
Result< R >	Invoke (A &&... args) const
	Call the property as a method of its object (otherwise the same as Value::Invoke()).
template<typename... A>
Result< Value >	operator() (A &&... args) const
	Call the property as a method: obj["save"](path) is the same as obj["save"].Invoke(path).
template<typename T>
Result< T >	To () const
	Read the property and convert it to a C++ type (see Value::To()).
template<typename T>
std::optional< T >	Maybe () const
	Read the property and convert it to a C++ type like To() but without the failure reason.
template<typename T>
T	Or (T fallback) const
	Read the property and convert it to a C++ type with a fallback.
std::string	Or (const char *fallback) const
	Read the property and convert it to a std::string with a string-literal fallback.
	Ref (const Ref &)=default
	Copy constructor (refers to the same property).
Ref &	operator= (const Ref &other)
	Set this property to the value of another Ref's property.

Friends
class	Value
class	Context

Constructor & Destructor Documentation

Ref()

Ref ( const Ref & )

default

Copy constructor (refers to the same property).

Member Function Documentation

Get()

Value Get ( ) const

inlinenodiscard

Read the property.

Returns

Returns the property value (an empty Value if the read fails, see Value::operator[]()).

Invoke()

template<typename R = Value, typename... A>

Result< R > Invoke

(

A &&...

args

)

const

Call the property as a method of its object (otherwise the same as Value::Invoke()).

global["JSON"]["stringify"](payload);
js::Result<double> total = cart["total"].Invoke<double>();

Parameters

args	The arguments to pass to the method.

Returns

Returns the call's result converted to R and fails the same way as Value::Invoke().

Maybe()

template<typename T>

std::optional< T > Maybe ( ) const

nodiscard

Read the property and convert it to a C++ type like To() but without the failure reason.

Returns

Returns the converted value or nullopt on any failure.

operator Value()

operator Value ( ) const

inline

Read the property (the same as Get()).

operator()()

template<typename... A>

Result< Value > operator() ( A &&... args ) const

inline

Call the property as a method: obj["save"](path) is the same as obj["save"].Invoke(path).

Parameters

args	The arguments to pass to the method.

Returns

Returns the call's result and fails the same way as Invoke().

operator=() [1/2]

Ref & operator= ( const Ref & other )

inline

Set this property to the value of another Ref's property.

Parameters

other

The Ref to read the value from.

Returns

Returns this Ref.

Note

A Ref always refers to the same property: assigning to it sets the property's value and never changes which property it refers to (like std::map's operator[]).

operator=() [2/2]

template<typename T>

Ref & operator=

(

T &&

value

)

Set the property to value (converted through js::TypeTraits).

Parameters

value

The value to assign.

Returns

Returns this Ref.

Note

Failures are ignored (eg, the page is gone or a setter throws). Use Value::SetProperty() if you need to check.

operator[]() [1/2]

Ref operator[] ( const char * name ) const

inline

Read this property and access a property of its value.

Parameters

name	The property name.

Returns

Returns a Ref for the nested property.

operator[]() [2/2]

template<typename I>
requires (std::is_integral_v<I> && !std::is_same_v<I, bool>)

Ref operator[] ( I index ) const

inline

Or() [1/2]

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

inlinenodiscard

Read the property and convert it to a std::string with a string-literal fallback.

Parameters

fallback

The text to return if the read or 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

Read the property and convert it to a C++ type with a fallback.

Parameters

fallback

The value to return if the read or the conversion fails.

Returns

Returns the converted value or fallback on any failure.

To()

template<typename T>

Result< T > To ( ) const

nodiscard

Read the property and convert it to a C++ type (see Value::To()).

Returns

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

Friends And Related Symbol Documentation

Context

friend class Context

friend

Value

friend class Value

friend

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

• Ultralight/js/Value.h