Programming Encapsulation (OCR A Level Computer Science): Revision Note

Programming Encapsulation

• To program encapsulation, you should already have a solid understanding of what encapsulation in Object Oriented Programming (OOP) is.

How do you Define Encapsulation?

Get Methods

• The "get" method is a common naming convention for a type of method that is used to retrieve the value of an object's private attributes (instance variables).

• These methods are also known as "getter" methods or "accessor" methods.

• The main purpose of a get method is to provide controlled access to the internal state (data) of an object without allowing direct modification.

• Attributes are often declared as private to achieve encapsulation, so cannot be accessed directly from outside the class.

• External code can use the public get methods to read the values of these private attributes (also known as instance variables).

Pseudocode

Pseudocode for a get method

Java

//creating a class called NumberUpdater

public class NumberUpdater {

    //setting the private attribute to the value of 10

    private int number = 10;

    //creating a get method that will return the value store in the number attribute

    public int getNumber() {

        return number;

    }

}

Python

#creating a class called NumberUpdater

class NumberUpdater:

    #setting the private attribute to the value of 10 

   def __init__(self):

        self.__number = 10

    #creating a get method that will return the value stored in the number attribute

    @property

    def number(self):

        return self.__number

Set Methods

• The "set" method is a common naming convention for a type of method that is used to set the value of object's private instance variables.

• Setter methods, also known as “setter” methods or “mutator” methods

• Generally additional code is written within the method to allow controlled access by enforcing certain conditions or validations before updating the attribute

Pseudocode

Pseudocode for a "setter" method

Java

//creating a class called NumberUpdater

public class NumberUpdater  

        //setting attribute value to 10

    private int oldnumber = 10;

    //creating a set method

    public void setNumber(int newnumber) {

         //if the new number is less than zero

      if (newnumber < 0) {

             //oldnumber is kept the same 

         oldnumber = oldnumber;

        } else {

            //oldnumber is updated with the new number value

               oldnumber = newnumber;

        }

    }

}

Python

//creating a class called NumberUpdater

class NumberUpdater:

     //setting attribute value to 10

   def __init__(self):

        self.__oldnumber = 10

     //creating a set method 

   def setNumber(self, newnumber):

       //if the new number is less than zero 

       if newnumber < 0:

                  //oldnumber is kept the same

            self.__oldnumber = self.__oldnumber

        else:

            //oldnumber is updated with the new number value   

                 self.__oldnumber = newnumber