What this course is about Learning and applying
- Slides: 9
What this course is about Learning and applying various creational, structural and behavioral Design Patterns to the design of software components and applications SE-2811 Dr. Mark L. Hornick 1
One goal of good software design is Reuse and Maintainability You already re-use code on low level l What are some examples? Code re-use is great, but it’s not a Design Patterns are about reuse on a higher level l Reuse of an approach, rather than specific classes and/or code SE-2811 Dr. Mark L. Hornick 2
Design Patterns are a higher level of abstraction than class libraries You are already familiar with designing and implementing various classes that each perform specific functions: l l l Application classes UI classes Data classes Design Patterns help us to figure out how to arrange classes to work together to solve problems that recur frequently. SE-2811 Dr. Mark L. Hornick 3
A Design Pattern is… A “standard” arrangement of certain classes that comprise a solution to a given problem l l Many different Patterns can appear in a single application Patterns are given common names, such as Strategy or Observer During execution, the objects created from these classes interact in a specific way to implement a specific function l l The same type of function that is typically needed by many types of applications The specific interactions are often defined by SE-2811 interfaces Dr. Mark L. Hornick 4
What problem does a Design Pattern solve? ? SE-2811 Dr. Mark L. Hornick 5
Design Patterns is partly about not reinventing the wheel every time you design a new application Instead, reuse well-accepted approaches…. . that are also easier to maintain, since the approach is well-understood SE-2811 Dr. Mark L. Hornick 6
A Design Pattern is… An approach to solving a problem that occurs over and over again in many different applications l l l But with context-specific variations when applied … so it’s not the same classes used over and over … but it’s a similar way of solving similar problems The core of a solution l The solution can be used many times over without ever doing it the same way twice SE-2811 Dr. Mark L. Hornick 7
Over the years, a number of “good” Design Patterns have been “discovered” The classes involved generally focus on doing a certain thing (high cohesion) And because they have low coupling (don’t require strong interaction with other classes), they can be dropped into you application l With some minor tailoring to fit your specific need SE-2811 Dr. Mark L. Hornick 8
Why should we learn Design Patterns? Shared vocabulary l l Allows to communicate not just qualities, but also characteristics and constraints that the pattern represents. Allow you to say more with less: saying “Observer Pattern” gets everyone on-board with the approach in two words. Helps you focus on the “design” l You do not get into the nitty-gritty details of implementation right away. Less room for misunderstanding l Improved productivity and quality 9
