ListenerList< ListenerClass, ArrayType > Class Template Reference
juce_core » containers

Holds a set of objects and can invoke a member function callback on each object in the set with a single call. More...

## Classes

struct | DummyBailOutChecker
| A dummy bail-out checker that always returns false. More...
struct | Iterator
| Iterates the listeners in a ListenerList. More...

## Public Types

using | ThisType = ListenerList< ListenerClass, ArrayType >
using | ListenerType = ListenerClass

## Public Member Functions

| ListenerList ()=default
| Creates an empty list. More...
| ~ListenerList ()=default
| Destructor. More...
void | add (ListenerClass *listenerToAdd)
| Adds a listener to the list. More...
void | remove (ListenerClass *listenerToRemove)
| Removes a listener from the list. More...
int | size () const noexcept
| Returns the number of registered listeners. More...
bool | isEmpty () const noexcept
| Returns true if no listeners are registered, false otherwise. More...
void | clear ()
| Clears the list. More...
bool | contains (ListenerClass *listener) const noexcept
| Returns true if the specified listener has been added to the list. More...
const ArrayType & | getListeners () const noexcept
| Returns the raw array of listeners. More...
template<typename Callback >
void | call (Callback &&callback)
| Calls a member function on each listener in the list, with multiple parameters. More...
template<typename Callback >
void | callExcluding (ListenerClass *listenerToExclude, Callback &&callback)
| Calls a member function with 1 parameter, on all but the specified listener in the list. More...
template<typename Callback , typename BailOutCheckerType >
void | callChecked (const BailOutCheckerType &bailOutChecker, Callback &&callback)
| Calls a member function on each listener in the list, with 1 parameter and a bail-out-checker. More...
template<typename Callback , typename BailOutCheckerType >
void | callCheckedExcluding (ListenerClass *listenerToExclude, const BailOutCheckerType &bailOutChecker, Callback &&callback)
| Calls a member function, with 1 parameter, on all but the specified listener in the list with a bail-out-checker. More...

## Detailed Description

### template<class ListenerClass, class ArrayType = Array<ListenerClass*>>
class ListenerList< ListenerClass, ArrayType >

Holds a set of objects and can invoke a member function callback on each object in the set with a single call.

Use a ListenerList to manage a set of objects which need a callback, and you can invoke a member function by simply calling call() or callChecked().

E.g.

class MyListenerType
{
public:
void myCallbackMethod (int foo, bool bar);
};
ListenerList<MyListenerType> listeners;
listeners.add (someCallbackObjects...);
// This will invoke myCallbackMethod (1234, true) on each of the objects
// in the list...
listeners.call ([] (MyListenerType& l) { l.myCallbackMethod (1234, true); });

If you add or remove listeners from the list during one of the callbacks - i.e. while it's in the middle of iterating the listeners, then it's guaranteed that no listeners will be mistakenly called after they've been removed, but it may mean that some of the listeners could be called more than once, or not at all, depending on the list's order.

Sometimes, there's a chance that invoking one of the callbacks might result in the list itself being deleted while it's still iterating - to survive this situation, you can use callChecked() instead of call(), passing it a local object to act as a "BailOutChecker". The BailOutChecker must implement a method of the form "bool shouldBailOut()", and the list will check this after each callback to determine whether it should abort the operation. For an example of a bail-out checker, see the Component::BailOutChecker class, which can be used to check when a Component has been deleted. See also ListenerList::DummyBailOutChecker, which is a dummy checker that always returns false.

## Member Typedef Documentation

## ThisType

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>

using ListenerList< ListenerClass, ArrayType >::ThisType = ListenerList<ListenerClass, ArrayType>

## ListenerType

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>

using ListenerList< ListenerClass, ArrayType >::ListenerType = ListenerClass

## Constructor & Destructor Documentation

## ListenerList()

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>

ListenerList< ListenerClass, ArrayType >::ListenerList | ( |  | ) |

default

Creates an empty list.

## ~ListenerList()

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>

ListenerList< ListenerClass, ArrayType >::~ListenerList | ( |  | ) |

default

Destructor.

## Member Function Documentation

## add()

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>

void ListenerList< ListenerClass, ArrayType >::add | ( | ListenerClass * | listenerToAdd | ) |

Adds a listener to the list.

A listener can only be added once, so if the listener is already in the list, this method has no effect.

See also
  remove

## remove()

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>

void ListenerList< ListenerClass, ArrayType >::remove | ( | ListenerClass * | listenerToRemove | ) |

Removes a listener from the list.

If the listener wasn't in the list, this has no effect.

## size()

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>

int ListenerList< ListenerClass, ArrayType >::size | ( |  | ) | const

noexcept

Returns the number of registered listeners.

## isEmpty()

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>

bool ListenerList< ListenerClass, ArrayType >::isEmpty | ( |  | ) | const

noexcept

Returns true if no listeners are registered, false otherwise.

## clear()

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>

void ListenerList< ListenerClass, ArrayType >::clear | ( |  | ) |

Clears the list.

## contains()

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>

bool ListenerList< ListenerClass, ArrayType >::contains | ( | ListenerClass * | listener | ) | const

noexcept

Returns true if the specified listener has been added to the list.

## getListeners()

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>

const ArrayType& ListenerList< ListenerClass, ArrayType >::getListeners | ( |  | ) | const

noexcept

Returns the raw array of listeners.

## call()

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>
template<typename Callback >

void ListenerList< ListenerClass, ArrayType >::call | ( | Callback && | callback | ) |

Calls a member function on each listener in the list, with multiple parameters.

## callExcluding()

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>
template<typename Callback >

void ListenerList< ListenerClass, ArrayType >::callExcluding | ( | ListenerClass * | listenerToExclude,
|  | Callback && | callback
| ) |  |

Calls a member function with 1 parameter, on all but the specified listener in the list.

This can be useful if the caller is also a listener and needs to exclude itself.

## callChecked()

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>
template<typename Callback , typename BailOutCheckerType >

void ListenerList< ListenerClass, ArrayType >::callChecked | ( | const BailOutCheckerType & | bailOutChecker,
|  | Callback && | callback
| ) |  |

Calls a member function on each listener in the list, with 1 parameter and a bail-out-checker.

See the class description for info about writing a bail-out checker.

## callCheckedExcluding()

template<class ListenerClass, class ArrayType = Array<ListenerClass*>>
template<typename Callback , typename BailOutCheckerType >

void ListenerList< ListenerClass, ArrayType >::callCheckedExcluding | ( | ListenerClass * | listenerToExclude,
|  | const BailOutCheckerType & | bailOutChecker,
|  | Callback && | callback
| ) |  |

Calls a member function, with 1 parameter, on all but the specified listener in the list with a bail-out-checker.

This can be useful if the caller is also a listener and needs to exclude itself. See the class description for info about writing a bail-out checker.

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

- juce_ListenerList.h

ListenerList::call
void call(Callback &&callback)
Calls a member function on each listener in the list, with multiple parameters.
Definition: juce_ListenerList.h:120
ListenerList
Holds a set of objects and can invoke a member function callback on each object in the set with a sin...
Definition: juce_ListenerList.h:69
ListenerList::add
void add(ListenerClass *listenerToAdd)
Adds a listener to the list.
Definition: juce_ListenerList.h:85