OOP
Last updated
Last updated
Following are the four pillars of OOP principle,
Encapsulation
Abstraction
Polymorphism
Inheritance
Encapsulation is a language construct that facilitates the bundling of data with the methods operating on that data.
Encapsulation doesn't guarantee data protection, cohesive design or information hiding.
Information hiding is a design principle that strives to shield client classes from the internal workings of a class.
Encapsulation facilitates, but does not guarantee, information hiding.
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Abstraction is preserving information that is relevant in a given context, and forgetting information that is irrelevant in that context.
The provision of a single interface to entities of different types or the use of a single symbol to represent multiple different types is known as polymorphism.
Major classes of polymorphism
Ad hoc polymorphism
Polymorphic functions that can be applied to arguments of different types, but that behave differently depending on the type of the argument to which they are applied.
Parametric polymorphism
A function or a data type to be written generically, so that it can handle values uniformly without depending on their type.
Parametric polymorphism is a way to make a language more expressive while still maintaining full static type-safety.
Subtype polymorphism
Subtyping allows a function to be written to take an object of a certain type T, but also work correctly, if passed an object that belongs to a type S that is a subtype of T (according to the Liskov substitution principle).
This type relation is sometimes written S <: T. Conversely, T is said to be a supertype of S—written T :> S. Subtype polymorphism is usually resolved dynamically.
Coercion polymorphism
Implicit type conversion by compiler aka type juggling is also a type of polymorphism.
Polymorphism can be distinguished by when the implementation is selected.
Static polymorphism typically occurs in ad hoc and parametric polymorphsim.
Dynamic poymorphism usually occurs in subtype polymorphism. But subtype polymorphism can be achieved through static polymorphism as well.
The mechanism of basing an object or class upon another object (prototype-based inheritance) or class (class-based inheritance), retaining similar implementation.
Also defined as deriving new classes (sub classes) from existing ones such as super class or base class and then forming them into a hierarchy of classes.
Inheritance only reuses implementation and establishes a syntactic relationship, not necessarily a semantic relationship (inheritance does not ensure behavioral subtyping).
The inheritance hierarchy of an object is fixed at instantiation when the object's type is selected and does not change with time.
Types of inheritance
Single
Multiple
Multilevel
Hierarchical
Hybrid
Subtyping enables a given type to be substituted for another type or abstraction, and is said to establish an is-a relationship between the subtype and some existing abstraction, either implicitly or explicitly, depending on language support.