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A very common example of code reuse is the technique of using a software library. Many common operations, such as converting information among different well-known formats, accessing external storage, interfacing with external programs, or manipulating information (numbers, words, names, locations, dates, etc.) in common ways, are needed by ...
The C++ examples in this section demonstrate the principle of using composition and interfaces to achieve code reuse and polymorphism. Due to the C++ language not having a dedicated keyword to declare interfaces, the following C++ example uses inheritance from a pure abstract base class.
Subroutines or functions are the simplest form of reuse. A chunk of code is regularly organized using modules or namespaces into layers . Proponents claim that objects and software components offer a more advanced form of reusability, although it has been tough to objectively measure and define levels or scores of reusability.
Libraries encourage code reuse in a modular fashion. When writing code that uses a library, a programmer only needs to know high-level information such as what items it contains at and how to use the items – not all of the internal details of the library. Libraries can use other libraries resulting in a hierarchy of libraries in a program.
In software engineering, the delegation pattern is an object-oriented design pattern that allows object composition to achieve the same code reuse as inheritance. In delegation, an object handles a request by delegating to a second object (the delegate). The delegate is a helper object, but with the original context.
For example, many web frameworks provide libraries for database access, templating frameworks, and session management, and they often promote code reuse. [1] Although they often target development of dynamic web sites , they are also applicable to static websites .
"Don't repeat yourself" (DRY), also known as "duplication is evil", is a principle of software development aimed at reducing repetition of information which is likely to change, replacing it with abstractions that are less likely to change, or using data normalization which avoids redundancy in the first place.
Design by contract can also facilitate code reuse, since the contract for each piece of code is fully documented. The contracts for a module can be regarded as a form of software documentation for the behavior of that module.