Editing Late binding (section)

{{Short description|When called functions or methods are looked up by name at runtime}}
{{About|associating a name with an operation|the selection of an implementation of a polymorphic operation|Dynamic dispatch}}
{{More citations needed|date=January 2011}}

In [[computing]], '''late binding''' or '''dynamic linkage'''<ref>{{Cite book|url=https://www.cs.rit.edu/~ats/books/ooc.pdf|title=Object-Oriented Programming With ANSI-C|last=Schreiner|first=Axel-Tobias|publisher=Hanser|year=1994|isbn=3-446-17426-5|location=Munich|pages=15}}</ref>—though not an identical process to [[Dynamic linker|dynamically linking]] imported code [[Library (computing)|libraries]]—is a [[computer programming]] mechanism in which the [[Method (computer programming)|method]] being called upon an [[Object (computer science)|object]], or the [[Subroutine|function]] being called with arguments, is looked up by name at [[Run time (program lifecycle phase)|runtime]]. In other words, a name is associated with a particular operation or object at runtime, rather than during [[Compiler|compilation]]. The name '''dynamic binding''' is sometimes used,<ref>Booch, Grady. Object-oriented Analysis and Design. Addison-Wesley, 1994. p71</ref> but is more commonly used to refer to [[dynamic scope]].

With [[early binding]], or [[static binding]], in an [[Object-oriented programming|object-oriented language]], the compilation phase fixes all [[Data type|types]] of [[Variable (computer science)|variables]] and [[Expression (computer science)|expressions]]. This is usually stored in the compiled program as an offset in a [[virtual method table]] ("v-table").<ref>{{cite web|url=http://support.microsoft.com/default.aspx?scid=kb;EN-US;245115|title=Using early binding and late binding in Automation|date= 2003-09-06|accessdate=2014-06-27|publisher=[[Microsoft]]|archive-url=https://web.archive.org/web/20140627041338/http://support.microsoft.com/default.aspx?scid=kb;EN-US;245115|archive-date=2014-06-27}}</ref> In contrast, with late binding, the compiler does not read enough information to verify the method exists or bind its slot on the v-table. Instead, the method is looked up by name at runtime.

The primary advantage of using late binding in [[Component Object Model]] (COM) programming is that it does not require the compiler to reference the libraries that contain the object at [[compile time]]. This makes the compilation process more resistant to version conflicts, in which the class's v-table may be accidentally modified. (This is not a concern in [[just-in-time compilation|just-in-time compiled]] platforms such as [[.NET]] or [[Java (programming language)|Java]], because the v-table is created at runtime by the [[virtual machine]] against the libraries as they are being loaded into the running application.<ref>{{cite web| url = http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-2.html#jvms-2.6.3| title = The Structure of the Java Virtual Machine: Dynamic Linking| year = 1999 | accessdate = 2013-09-21| at = sec. 3.6.3| publisher = [[Sun Microsystems]]}}</ref>)