Editing Duck typing (section)

===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.