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All these languages allow classes to implement multiple protocols. Moreover, Ada, C#, Java, Object Pascal, Objective-C, Swift and PHP allow multiple-inheritance of interfaces (called protocols in Objective-C and Swift). Interfaces are like abstract base classes that specify method signatures without implementing any behaviour.
In languages supporting multiple inheritance, such as C++, interfaces are implemented as abstract classes. In languages without explicit support, protocols are often still present as conventions. This is known as duck typing. For example, in Python, any class can implement an __iter__ method and be used as a collection. [3]
The relationships are specified in the science of object-oriented design and object interface standards defined by popular use, language designers (Java, C++, Smalltalk, Visual Prolog) and standards committees for software design like the Object Management Group. The class hierarchy can be as deep as needed.
Composition over inheritance (or composite reuse principle) in object-oriented programming (OOP) is the principle that classes should favor polymorphic behavior and code reuse by their composition (by containing instances of other classes that implement the desired functionality) over inheritance from a base or parent class. [2]
Not all languages support multiple inheritance. For example, Java allows a class to implement multiple interfaces, but only inherit from one class. [22] If multiple inheritance is allowed, the hierarchy is a directed acyclic graph (or DAG for short), otherwise it is a tree. The hierarchy has classes as nodes and inheritance relationships as links.
Those design decisions do not always map to other languages easily. For instance, classes using multiple inheritance from a language that permits it will not translate well to a language that does not permit multiple inheritance. A common approach to this issue is defining a subset of a language that is compatible with another language's ...
Multiple inheritance where one class can have more than one superclass and inherit features from all parent classes. "Multiple inheritance ... was widely supposed to be very difficult to implement efficiently. For example, in a summary of C++ in his book on Objective C, Brad Cox actually claimed that adding multiple inheritance to C++ was ...
In the Curl web-content language, multiple inheritance is used as classes with no instances may implement methods. Common mixins include all skinnable ControlUI s inheriting from SkinnableControlUI , user interface delegate objects that require dropdown menus inheriting from StandardBaseDropdownUI and such explicitly named mixin classes as ...