In contrast to Meyer's usage, this definition advocates inheritance from abstract base classes. Polymorphic open–closed principle ĭuring the 1990s, the open–closed principle became popularly redefined to refer to the use of abstracted interfaces, where the implementations can be changed and multiple implementations could be created and polymorphically substituted for each other. When a descendant class is defined, there is no need to change the original or to disturb its clients. But it is also open, since any new class may use it as parent, adding new features. Meyer's proposed solution to this dilemma relied on the notion of object-oriented inheritance (specifically implementation inheritance): : 229Ī class is closed, since it may be compiled, stored in a library, baselined, and used by client classes. This assumes that the module has been given a well-defined, stable description (the interface in the sense of information hiding).Īt the time Meyer was writing, adding fields or functions to a library inevitably required changes to any programs depending on that library. A module will be said to be closed if is available for use by other modules.For example, it should be possible to add fields to the data structures it contains, or new elements to the set of functions it performs. A module will be said to be open if it is still available for extension.

Open–closed principle is one of the five SOLID principles of object-oriented design.īertrand Meyer is generally credited for having originated the term open–closed principle, which appeared in his 1988 book Object Oriented Software Construction. Both ways use generalizations (for instance, inheritance or delegate functions) to resolve the apparent dilemma, but the goals, techniques, and results are different. The name open–closed principle has been used in two ways. That is, such an entity can allow its behaviour to be extended without modifying its source code.

In object-oriented programming, the open–closed principle (OCP) states ' software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification'

Oo software shut up