Callback (computer programming)

In computer programming, a callback is a piece of executable code that is passed as an argument to other code, which is expected to call back (execute) the argument at some convenient time.

Description

The invocation may be immediate as in a synchronous callback, or it might happen at a later time as in an asynchronous callback.

In all cases, the intention is to specify a function or subroutine as an entity that is, depending on the language, more or less similar to a variable.

Programming languages support callbacks in different ways, often implementing them with subroutines, lambda expressions, blocks, or function pointers.

See also

• Command pattern
• Computer programming
• Continuation-passing style
• Event loop
• Event-driven programming
• Function (programming) - a sequence of program instructions that perform a specific task, packaged as a unit.
• Futures and promises
• Implicit invocation
• Inversion of control
• Parameter (computer programming)
• Signals and slots
• User exit
• Variable (computer science)

External links

• Callback (computer programming @ Wikipedia
• Callback Hell
• A Story About Callbacks @ commitstrip.com