Editing Duck typing (section)

==Comparison with other type systems==

===Structural type systems===

Duck typing is similar to, but distinct from, [[Structural type system|structural typing]]. Structural typing is a [[Type system#Static typing|static typing]] system that determines type compatibility and equivalence by a type's structure, whereas duck typing is [[Type system#Dynamic typing|dynamic]] and determines type compatibility by only that part of a type's structure that is accessed during [[Runtime (program lifecycle phase)|runtime]].

The [[TypeScript]],<ref>{{Cite web|url=https://www.se-radio.net/2019/10/episode-384-boris-cherny-on-typescript|title=SE Radio Episode 384: Boris Cherny on TypeScript|website=se-radio.net|access-date=2019-10-25}}</ref> [[Elm (programming language)|Elm]]<ref>{{cite web|url=http://guide.elm-lang.org/core_language.html|title=Core Language · An Introduction to Elm|first=Evan|last=Czaplicki|access-date=30 January 2017}}</ref> and [[Python (programming language)|Python]]<ref>{{Cite web|url=https://peps.python.org/pep-0544/|title=PEP 544 – Protocols: Structural subtyping (static duck typing)}}</ref> languages support structural typing to varying degrees.

===Protocols and interfaces===

[[Interface (object-oriented programming)|Protocols and interfaces]] provide a way to explicitly declare that some methods, operators or behaviors must be defined. If a third-party library implements a class that cannot be modified, a client cannot use an instance of it with an interface unknown to that library even if the class satisfies the interface requirements. A common solution to this problem is the [[adapter pattern]]. In contrast, with duck typing, the object would be accepted directly without the need for an adapter.

===Templates or generic types===

[[Template metaprogramming|Template]] (also called [[Generic programming|generic]]) functions or methods apply the duck test in a [[Type system#Static typing|static typing]] context; this brings all of the advantages and disadvantages of [[Type system#Static and dynamic type checking in practice|static versus dynamic type checking]]. Duck typing can also be more flexible in that only the methods actually called at runtime must be implemented, while templates require implementations of all methods that cannot be proven [[Unreachable code|unreachable]] at compile time.

In languages such as Java, Scala and Objective-C, [[reflection (computer programming)|reflection]] may be employed to inspect whether objects implement methods or add necessary methods at runtime. For example, [[Java (programming language)|Java]]'s MethodHandle API can be used in this manner.<ref>{{cite web|url=https://stackoverflow.com/questions/62321273/implement-duck-typing-using-java-methodhandles|title=StackOverflow: Implement duck typing using java MethodHandles|access-date=13 June 2020}}</ref>