Value Class Reference

Represents a shared variant value. More...

#include <juce_Value.h>

Collaboration diagram for Value:

Classes
class	Listener
	Receives callbacks when a Value object changes. More...
class	ValueSource
	Used internally by the Value class as the base class for its shared value objects. More...

Public Member Functions
	Value ()
	Creates an empty Value, containing a void var. More...
	Value (const Value &other)
	Creates a Value that refers to the same value as another one. More...
	Value (const var &initialValue)
	Creates a Value that is set to the specified value. More...
	Value (Value &&) noexcept
	Move constructor. More...
	Value (ValueSource *valueSource)
	Creates a Value object that uses this valueSource object as its underlying data. More...
	~Value ()
	Destructor. More...
void	addListener (Listener *listener)
	Adds a listener to receive callbacks when the value changes. More...
var	getValue () const
	Returns the current value. More...
ValueSource &	getValueSource () noexcept
	Returns the ValueSource that this value is referring to. More...
	operator var () const
	Returns the current value. More...
bool	operator!= (const Value &other) const
	Compares two values. More...
Value &	operator= (const var &newValue)
	Sets the current value. More...
Value &	operator= (Value &&) noexcept
	Move assignment operator. More...
bool	operator== (const Value &other) const
	Compares two values. More...
bool	refersToSameSourceAs (const Value &other) const
	Returns true if this value and the other one are references to the same value. More...
void	referTo (const Value &valueToReferTo)
	Makes this object refer to the same underlying ValueSource as another one. More...
void	removeListener (Listener *listener)
	Removes a listener that was previously added with addListener(). More...
void	setValue (const var &newValue)
	Sets the current value. More...
String	toString () const
	Returns the value as a string. More...

Private Member Functions
	Value (void *) JUCE_DELETED_FUNCTION
void	callListeners ()
Value &	operator= (const Value &) JUCE_DELETED_FUNCTION
void	removeFromListenerList ()

Private Attributes
ListenerList< Listener >	listeners
ReferenceCountedObjectPtr< ValueSource >	value

Friends
class	ValueSource

Detailed Description

Represents a shared variant value.

A Value object contains a reference to a var object, and can get and set its value. Listeners can be attached to be told when the value is changed.

The Value class is a wrapper around a shared, reference-counted underlying data object - this means that multiple Value objects can all refer to the same piece of data, allowing all of them to be notified when any of them changes it.

When you create a Value with its default constructor, it acts as a wrapper around a simple var object, but by creating a Value that refers to a custom subclass of ValueSource, you can map the Value onto any kind of underlying data.

Important note! The Value class is not thread-safe! If you're accessing one from multiple threads, then you'll need to use your own synchronisation around any code that accesses it.

Constructor & Destructor Documentation

Value() [1/6]

Value::Value

(

)

Creates an empty Value, containing a void var.

Value() [2/6]

Value::Value

(

const Value &

other

)

Creates a Value that refers to the same value as another one.

Note that this doesn't make a copy of the other value - both this and the other Value will share the same underlying value, so that when either one alters it, both will see it change.

Value() [3/6]

Value::Value ( const var &  initialValue )

explicit

Creates a Value that is set to the specified value.

Value() [4/6]

Value::Value ( Value &&  )

noexcept

Move constructor.

~Value()

Value::~Value

(

)

Destructor.

Value() [5/6]

Value::Value ( ValueSource *  valueSource )

explicit

Creates a Value object that uses this valueSource object as its underlying data.

Value() [6/6]

Value::Value ( void *  )

explicitprivate

Member Function Documentation

addListener()

void Value::addListener

(

Listener *

listener

)

Adds a listener to receive callbacks when the value changes.

The listener is added to this specific Value object, and not to the shared object that it refers to. When this object is deleted, all the listeners will be lost, even if other references to the same Value still exist. So when you're adding a listener, make sure that you add it to a Value instance that will last for as long as you need the listener. In general, you'd never want to add a listener to a local stack-based Value, but more likely to one that's a member variable.

See also

removeListener

Referenced by StandaloneFilterWindow::MainContentComponent::MainContentComponent().

callListeners()

void Value::callListeners ( )

private

getValue()

var Value::getValue

(

)

const

Returns the current value.

Referenced by StandalonePluginHolder::audioDeviceIOCallback(), StandaloneFilterWindow::MainContentComponent::MainContentComponent(), StandalonePluginHolder::saveAudioDeviceState(), and StandaloneFilterWindow::MainContentComponent::valueChanged().

getValueSource()

ValueSource& Value::getValueSource ( )

inlinenoexcept

Returns the ValueSource that this value is referring to.

References value.

operator var()

Value::operator var

(

)

const

Returns the current value.

operator!=()

bool Value::operator!=

(

const Value &

other

)

const

Compares two values.

This is a compare-by-value comparison, so is effectively the same as saying (this->getValue() != other.getValue()).

operator=() [1/3]

Value& Value::operator=

(

const var &

newValue

)

Sets the current value.

This is the same as calling setValue().

If there are any listeners registered, they will be notified of the change asynchronously.

operator=() [2/3]

Value& Value::operator= ( Value &&  )

noexcept

Move assignment operator.

operator=() [3/3]

Value& Value::operator= ( const Value &  )

private

operator==()

bool Value::operator==

(

const Value &

other

)

const

Compares two values.

This is a compare-by-value comparison, so is effectively the same as saying (this->getValue() == other.getValue()).

refersToSameSourceAs()

bool Value::refersToSameSourceAs

(

const Value &

other

)

const

Returns true if this value and the other one are references to the same value.

referTo()

void Value::referTo

(

const Value &

valueToReferTo

)

Makes this object refer to the same underlying ValueSource as another one.

Once this object has been connected to another one, changing either one will update the other.

Existing listeners will still be registered after you call this method, and they'll continue to receive messages when the new value changes.

removeFromListenerList()

void Value::removeFromListenerList ( )

private

removeListener()

void Value::removeListener

(

Listener *

listener

)

Removes a listener that was previously added with addListener().

setValue()

void Value::setValue

(

const var &

newValue

)

Sets the current value.

You can also use operator= to set the value.

If there are any listeners registered, they will be notified of the change asynchronously.

Referenced by StandalonePluginHolder::reloadAudioDeviceState().

toString()

String Value::toString

(

)

const

Returns the value as a string.

This is a shortcut for "myValue.getValue().toString()".

Friends And Related Function Documentation

ValueSource

friend class ValueSource

friend

Member Data Documentation

listeners

ListenerList<Listener> Value::listeners

private

value

ReferenceCountedObjectPtr<ValueSource> Value::value

private

Referenced by getValueSource().

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

• juce_Value.h