Software Development. Modular Design and Algorithm Analysis

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1 Software Development Modular Design and Algorithm Analysis

2 Data Encapsulation Encapsulation is the packing of data and functions into a single component. The features of encapsulation are supported using classes in most object-oriented programming languages, although other alternatives also exist. It allows selective hiding of properties and methods in an object by building an impenetrable wall to protect the code from accidental corruption. In programming languages, encapsulation is used to refer to one of two related but distinct notions, and sometimes to the combination thereof:

3 1. A language mechanism for restricting access to some of the object's components. 2. A language construct that facilitates the bundling of data with the methods (or other functions) operating on that data.

4 General definition In general, encapsulation is one of the four fundamentals of OOP (object-oriented programming). Encapsulation refers to the bundling of data with the methods that operate on that data. Encapsulation is used to hide the values or state of a structured data object inside a class, preventing unauthorized parties' direct access to them. Publicly accessible methods are generally provided in the class (so-called getters and setters) to access the values, and other client classes call these methods to retrieve and modify the values within the object.

5 Encapsulation is one of the most important and most advantageous concepts provided in object-oriented programming. By taking proper care when designing your objects to hide their internal details from the rest of the system, you gain the ability to simplify the remainder of the system while isolating it from problems caused by changes to the internal structure of your objects. These concepts are absolutely critical when working with a team.

6 Designing Strategy Most of us have learned through bitter experience to make class members private by default unless we really need to expose them. That's just good encapsulation. This wisdom is applied most frequently to data members, but it applies equally to all members, including virtual functions.

7 Reusability (Inheritance) In computer science and software engineering, reusability is the use of existing assets in some form within the software product development process. More than just code, assets are products and by-products of the software development life cycle and include software components, test suites, designs and documentation. Leverage is modifying existing assets as needed to meet specific system requirements.

8 Because reuse implies the creation of a separately maintained version of the assets, it is preferred over leverage. 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.

9 The ability to reuse relies in an essential way on the ability to build larger things from smaller parts, and being able to identify commonalities among those parts. Reusability is often a required characteristic of platform software. Reusability brings several aspects to software development that do not need to be considered when reusability is not required.

10 Reusability implies some explicit management of build, packaging, distribution, installation, configuration, deployment, maintenance and upgrade issues. If these issues are not considered, software may appear to be reusable from design point of view, but will not be reused in practice. Software reusability more specifically refers to design features of a software element (or collection of software elements) that enhance its suitability for reuse.

11 Some design features for software reuse include: Adaptable Brief: small size Consistency Correctness Fast Flexible Generic Modularity Simple: low complexity Stability under changing requirements

12 Inheritance enables new classes to receive or inherit the properties and methods of existing classes. Using two concepts of inheritance, subclassing (making a new class based on a previous one) and overriding (changing how a previous class works), you can organize your objects into a hierarchy. Using inheritance to make this hierarchy often creates easier to understand code, but most importantly it allows you to reuse and organize code more effectively.

13 In object-oriented programming, inheritance enables new objects to take on the properties of existing objects. A class that is used as the basis for inheritance is called a superclass or base class. A class that inherits from a superclass is called a subclass or derived class. The terms parent class and child class are also acceptable terms to use respectively. A child inherits visible properties and methods from its parent while adding additional properties and methods of its own.

14 Inheritance and controlling access The access level of a declared element is the extent of the ability to access it, that is, what code has permission to read it or write to it. This is determined not only by how you declare the element itself, but also by the access level of the element's container. Code that cannot access a containing element cannot access any of its contained elements, even those declared as Public.

15 For example, a Public variable in a Private structure can be accessed from inside the class that contains the structure, but not from outside that class. The Public keyword in the declaration statement specifies that the elements can be accessed from code anywhere in the same project, from other projects that reference the project, and from any assembly built from the project. You can use Public only at module, interface, or namespace level. This means you can declare a public element at the level of a source file or namespace, or inside an interface, module, class, or structure, but not in a procedure.

16 The Protected keyword in the declaration statement specifies that the elements can be accessed only from within the same class, or from a class derived from this class. You can use Protected only at class level, and only when you declare a member of a class. This means you can declare a protected element in a class, but not at the level of a source file or namespace, or inside an interface, module, structure, or procedure.

17 The Friend keyword in the declaration statement specifies that the elements can be accessed from within the same assembly, but not from outside the assembly. You can use Friend only at module, interface, or namespace level. This means you can declare a friend element at the level of a source file or namespace, or inside an interface, module, class, or structure, but not in a procedure.

18 The Protected and Friend keywords together in the declaration statement specify that the elements can be accessed either from derived classes or from within the same assembly, or both. You can use Protected Friend only at class level, and only when you declare a member of a class. This means you can declare a protected friend element in a class, but not at the level of a source file or namespace, or inside an interface, module, structure, or procedure.

19 The Private keyword in the declaration statement specifies that the elements can be accessed only from within the same module, class, or structure. You can use Private only at module level. This means you can declare a private element inside a module, class, or structure, but not at the level of a source file or namespace, inside an interface, or in a procedure. At the module level, the Dim statement without any access level keywords is equivalent to a Private declaration. However, you might want to use the Private keyword to make your code easier to read and interpret.

Activity 3.5 Using the information in the presentation, apply reusability, inheritance and encapsulation when designing new classes and modules.

20 Activity 3.5 Using the information in the presentation, apply reusability, inheritance and encapsulation when designing new classes and modules. Copy examples of these three principles with a brief description on how you attained them into a document. You may need to wait until you have more of your culminating activity completed before you have the code you need. Save your work as john_s_3_5_peri under the appropriate folder for your class in the DropOff folder on the X: drive

Chapter 5 Object-Oriented Programming

Chapter 5 Object-Oriented Programming Develop code that implements tight encapsulation, loose coupling, and high cohesion Develop code that demonstrates the use of polymorphism Develop code that declares