# sigc::signal_base Struct Reference
[Signals]

Base class for the sigc::signal# templates. More...

`#include <sigc++/signal_base.h>`

Inheritance diagram for sigc::signal_base:
[legend]

List of all members.

## Public Types
typedef size_t | size_type
## Public Member Functions
| signal_base (const signal_base& src)
signal_base& | operator= (const signal_base& src)
bool | empty () const
| Returns whether the list of slots is empty.
void | clear ()
| Empties the list of slots.
size_type | size () const
| Returns the number of slots in the list.
## Protected Types
typedef internal::signal_impl::iterator_type | iterator_type
## Protected Member Functions
iterator_type | connect (const slot_base& slot_)
| Adds a slot at the end of the list of slots.
iterator_type | insert (iterator_type i, const slot_base& slot_)
| Adds a slot at the given position into the list of slots.
iterator_type | erase (iterator_type i)
| Removes the slot at the given position from the list of slots.
internal::signal_impl* | impl () const
| Returns the signal_impl object encapsulating the list of slots.
## Protected Attributes
internal::signal_impl* | impl_
| The signal_impl object encapsulating the slot list.

## Detailed Description

Base class for the sigc::signal# templates.

signal_base integrates most of the interface of the derived sigc::signal# templates. The implementation, however, resides in sigc::internal::signal_impl. A sigc::internal::signal_impl object is dynamically allocated from signal_base when first connecting a slot to the signal. This ensures that empty signals don't waste memory.

## Member Function Documentation

iterator_type sigc::signal_base::connect | ( | const slot_base& | slot_ | ) | `[protected]`

Adds a slot at the end of the list of slots.

With connect(), slots can also be added during signal emission. In this case, they won't be executed until the next emission occurs.

Parameters:

  | slot_ | The slot to add to the list of slots.

Returns:
  An iterator pointing to the new slot in the list.

bool sigc::signal_base::empty | ( |  | ) | const`[inline]`

Returns whether the list of slots is empty.

Returns:
  `true` if the list of slots is empty.

iterator_type sigc::signal_base::erase | ( | iterator_type | i | ) | `[protected]`

Removes the slot at the given position from the list of slots.

Note that this function does not work during signal emission!

Parameters:

  | i | An iterator pointing to the slot to be removed.

Returns:
  An iterator pointing to the slot in the list after the one removed.

internal::signal_impl* sigc::signal_base::impl | ( |  | ) | const`[protected]`

Returns the signal_impl object encapsulating the list of slots.

Returns:
  The signal_impl object encapsulating the list of slots.

iterator_type sigc::signal_base::insert | ( | iterator_type | i,
|  | const slot_base& | slot_ |
| ) |  |  | `[protected]`

Adds a slot at the given position into the list of slots.

Note that this function does not work during signal emission!

Parameters:

  | i | An iterator indicating the position where slot_ should be inserted.
  | slot_ | The slot to add to the list of slots.

Returns:
  An iterator pointing to the new slot in the list.

size_type sigc::signal_base::size | ( |  | ) | const

Returns the number of slots in the list.

Returns:
  The number of slots in the list.