Signals and slots
Signals and slots is a language construct introduced in
The signal/slot system fits well with the way graphical user interfaces are designed.[citation needed] Similarly, the signal/slot system can be used for other non-GUI usages, for example asynchronous I/O (including sockets, pipes, serial devices, etc.) event notification or to associate timeout events with appropriate object instances and methods or functions. It is easy to use and no registration/deregistration/invocation code need to be written, because Qt's metaobject compiler (MOC) automatically generates the needed infrastructure.
A spreadsheet programs update system could be implemented using signals and slots such that when a cell is changed, its dependent cells are notified/updated.
Alternative implementations
This section may require cleanup to meet Wikipedia's quality standards. The specific problem is: Too many alternative implementations without describing what signal/slot is. (July 2013) |
There are some implementations of signal/slot systems based on C++ templates, which don't require the extra metaobject compiler, as used by Qt, such as libsigc++, sigslot, vdk-signals, nano-signal-slot, neosigslot, Signals, boost.signals2, Synapse, Cpp::Events, Platinum, JBroadcaster and KDBindings. Common Language Infrastructure (CLI) languages such as C# also supports a similar construct although with a different terminology and syntax: events play the role of signals, and delegates are the slots. Another implementation of signals exists for ActionScript 3.0, inspired by C# events and signals/slots in Qt. Additionally, a delegate can be a local variable, much like a function pointer, while a slot in Qt must be a class member declared as such. The C based GObject system also provides similar functionality via GSignal. In D it is implemented by std.signals.
See also
Libraries
Java: sig4j - multi-threaded, type-safe, based on the FunctionalInterface annotation introduced in Java 8.
C++: vdk-signals - thread-safe, type-safe, written in C++11 with atomic variables.
References
- ^ "Signals & Slots - QtCore 5.1". Qt Project. 2013-07-04. Retrieved 2013-07-04.