Encapsulation

Encapsulation

• 2.
  Encapsulation  “ toenclose in or as in a capsule ”  The object-oriented meaning of encapsulation is  to enclose related data, routines and definitions in a class capsule. This does not necessarily mean hiding. (Mish)  Encapsulation is the ‘bundling together’ of data and behavior so that they are inseparable. (Mcgraw Hill)
• 3.
  Why Encapsulation calledInformation Hiding  Encapsulation (also called information hiding) consists of separating the external aspects of an object, from the internal implementation details of the object, which are hidden from other objects.  Encapsulation prevents a program from becoming to interdependent that a small change has massive ripple effects.  Encapsulation has ability to combine data structure and behavior in a single entity makes encapsulation cleaner and more powerful than in conventional languages that separate data structure and behavior.
• 4.
  Information Hiding  InformationHiding: a module is characterized by the information it hides from other modules, which are called its clients. The hidden information remains a secret to the client modules. (Ghezzi et al)  Information hiding is the principle that users of a software component (such as a class) need to know only the essential details of how to initialize and access the component, and do not need to know the details of the implementation. (Budd)
• 5.
  What Encapsulation Providesin OO?  The interface is the visible surface of the capsule.  The interface describes the essential characteristics of objects of the class which are visible to the exterior world.  Interface data – which should be visible from outside/other class or method.  The implementation is hidden in the capsule.  The implementation hiding means that data can only be manipulated, that is updated, within the class, but it does not mean hiding interface data.  Implementation data – which should be hidden from outside/other class or method.
• 6.
  Public Member AccessSpecifier Private Member Access Specifier Protected Member Access Specifier
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  Public Member AccessSpecifier  Syntax  public: <declarations>  Description:  A public member can be accessed by any function.  Members of a struct or union are public by default.  You can override the default struct access with private or protected but you cannot override the default union access.  Friend declarations are not affected by these access specifiers.
• 8.
  Private Member AccessSpecifier  Syntax  private: <declarations>  Description:  A private member can be accessed only by member functions and friends of the class in which it is declared.  Class members are private by default.  You can override the default struct access with private or protected but you cannot override the default union access.  Friend declarations are not affected by these access specifiers.
• 9.
  Protect Member AccessSpecifier  Syntax  protected: <declarations>  Description:  A protected member can be accessed by member functions and friends of the class in which it was declared, and by classes derived (derived classes) from the declared class.  You can override the default struct access with private or protected but you cannot override the default union access.  Friend declarations are not affected by these access specifiers.
• 10.
  Example: Access Specifiers classMyClass { public: //access from anywhere int x; private: //only access from within a class int y; protected: //access from within a class ,or derived class int z; }; void main() { MyClass CopyClass; CopyClass.x = 1; //OK, Public Access. CopyClass.y = 2; //Error! Y isn't a member of MyClass CopyClass.z = 3; //Error! Z isn't a member of MyClass
• 11.
  Advantage of Encapsulation It prevents others accessing the insides of an object.  The only thing that can manipulate the data in an object is that object’s method or member function.  It main aim is to prevent accident.  It builds a protective wall (encapsulation) around the member data and member function of the class, and hiding implementation details of object. So It keeps data safe from accident.
• 12.
  Example: Encapsulation OrInformation Hiding (1/3) #include <iostream> // Declaration of the Box class. class Box { private: int height, width, depth; // private data members. public: Box(int, int, int);// constructor function. ~Box(); // destructor function. int volume(); // member function (compute volume). };
• 13.
  Example: Encapsulation OrInformation Hiding (2/3) // Definition of the Box class. Box::Box(int ht, int wd, int dp)// The constructor function. { height = ht; width = wd; depth = dp; } Box::~Box() //The destructor function. Use of scope resolution ‘::’ { // does nothing } int Box::volume() // Member function to compute the Box's volume. { return height * width * depth;
• 14.
  Example: Encapsulation OrInformation Hiding (3/3) // The main() function. int main() { // Construct a Box object. Box thisbox(7, 8, 9); // actual values // Compute and display the object's volume. int volume = thisbox.volume(); cout << “output volume is : “ << volume; return 0; } RESULT: output volume is: 504