Design patterns

1. Design Patterns
Khaled kamara

2. 1. Software crisis
2. How to be a better developer
3. Solving A problem
4. What and why Design patterns
5. Let’s code a game together
6. What else
7. How can you select the right design pattern
8. Some useful Design patterns for Graduation project
9. Architectural Pattern
10.Snap on software Architecture
Table of Content

3. Software crisis
Most software projects
fail completely or
partially because they
don’t meet all their
requirements. These
requirements can be
the cost, schedule,
quality, or
requirements
objectives. According
to many studies, the
failure rate of software
projects ranges
between 50% – 80%.

5. Data structure
Software engineering
Design Principles & Solid
Modern Architecture
Clean Code & Code Complexity
Best Practice&Generics
Design patterns

6. Patterns is
everywhere

7. Let’s make the Balloon Float

9. What is Design patterns
A standard solution to a common software problem in a
context.
▪ describes a recurring software structure or idiom
▪ is abstract from any particular programming language
▪ identifies classes and their roles in the solution to a problem
Same problem Different implementation

10. Benefits of using Design patterns
• Patterns give a design common vocabulary for software
design:
▪ Allows engineers to abstract a problem and talk about that
abstraction in isolation from its implementation.
▪ A culture; domain-specific patterns increase design speed.
• Capture expertise and allow it to be communicated:
▪ Promotes design reuse and avoid mistakes.
▪ Makes it easier for other developers to understand a system.
• Improve documentation (less is needed):
▪ Improve understandability (patterns are described well, once).
The change is the only fact

11. GOF
• in 1990 a group called the
Gang of Four or "GoF"
(Gamma, Helm, Johnson,
Vlissides) compile a
catalog of design patterns
o 1995 book Design Patterns:
Elements of Reusable
Object-Oriented
Software is a classic of the
field

13. Singleton
• intent: Ensure a class has only
one instance and provide a
global point of access to it
• Problem: How can we
guarantee that one and only
one instance of a class can be
created
• Solution

14. Types of Design patterns .
Creational
Simple Factory,Factory Method,Abstract
Factory,Builder,Prototype,Singleton
Behavioral
Chain of Responsibility,Command,Iterator,Mediator,
Memento,Observer,Visitor,Strategy,State, Template
Method
Structure
Adapter,Bridge,Composite,Decorator,Facade,
Flyweight,Proxy

15. Let’s Develop a game

16. Game Story
A game of a fighter walking in Road, facing random
enemies, Finding New Weapons and health potions.You
can choose different culture (pharos, bableons, Grease).
In case Fighter got spelled, it will affect his speed Very
slow or very fast.
Fighter has one check point in the middle of every level to
save his state, to return any time he want.
Every level up upgrade age(Stone age, Iron Age).

17. 1. fighter
2. Enemies
3. culture
4. Potions
5. Level up
6. restart level
7. Checkpoint
8. Spells
9. New ages
Key Words

18. To create fighter you
need to go throw the
fighter wizard in which
you can choose Fighter
gender and type.
every user has 1000 Coin
you can purchase weapon
and armor that affect
can increase health or
strength
fighter

19. Builder

20. Intent
construct complex objects step by step. Also allows you to
produce different types and representations of an object using
the same construction code.
Problem
step-by-step initialization of many fields and nested objects.
Such initialization code is usually buried inside a monstrous
constructor with lots of parameters. Or even worse: scattered all
over the client code.
Solution:
Builder

21. We have many enemies in
the game with different
types and power.
Each level can has certain
number of each enemy
Enemies

22. Factory

23. Intent
Creating complex object by the simplest way,encapsulate whats vary
or adding logic to creation.
Problem
Creating the object is different or expensive, repetitive code,
Solution:
Factory

24. We have many culture
supported,
Culture is a theme for
the fighter ,enemies,
weapons, armos, flags
and colors
Culture

25. Bridge

26. Intent
split a large class or a set of
closely related classes into two
separate hierarchies—abstraction
and implementation—which can be
developed independently of each
other.
Problem
Merging classes can be messy
Solution:
Bridge

27. Fighter can find Potions
that improve his strength
or Armor
Potions

28. Decorator

29. Intent
Decorator is a structural design pattern that lets you attach new
behaviors to objects by placing these objects inside special wrapper
objects that contain the behaviors.
Problem
Imagine that you’re working on a notification library which lets other
programs notify their users about important events.
Solution:
Decorator

30. To restart level or to
create new level we have
many steps,
Like creating new
enemies, loading Page
celebrate if new level ,
say ooh if restart level
...etc
Level Up

31. facade

32. Intent
provides a simplified interface to a library, a framework, or any
other complex set of classes,User does not need to know all our
steps, just want my app to work
Problem
Functions can vary,can be from different source
Solution:
facade

33. The Game has many check
point, when the user
reach it he can save the
state ,in case he lost his
live or close the game he
can come back to this
point
Save CheckPoint

34. Memento

35. Also known as: Snapshot
Intent
save and restore the previous state of an object without revealing
the details of its implementation.
Problem
Want to come Back to the old State,simplest way.
Solution:
Memento

36. Enemies can cast
Spells on our fighter,
that can affect
fighter speed
Spells

37. State

38. Intent
lets an object alter its behavior when its internal state changes. It
appears as if the object changed its class.
Problem
The main idea is that, at any given moment, there’s a finite number
of states which a program can be in. Within any unique state, the
program behaves differently, and the program can be switched from
one state to another instantaneously.
Solution:
State

39. Every Level Introduce a
new Age, Every Age Steps
work in a different way to
create a unique Game
Board ,Enemies ,weapons,
armors and potions
Introduce New Age

40. Template

41. Intent
defines the skeleton of an algorithm in the superclass but lets
subclasses override specific steps of the algorithm without changing
its structure.
Problem
To handle the code in a different way, system will need to create a
lot of classes that will be redundant
Solution:
Template

42. Do not overuse the patterns
Overusing the patterns,can
Complicate our Code.
One million dollar Pen
In the cold war between america
and russia there was a space war,
astronauts needed pens to write,
american scientist invented a pen
that cost million dollar.
While russian write in pencil
CarGo Cult Programming

43. 1. Identify the problem
2. Review the existing patterns
3. Evaluate the pros and cons
4. Apply the pattern
How can you select the right design pattern for your project?
We can use part of design
pattern to solve the problem or
combine between them.

44. Are there more design
patterns than the 23 of
Gang oF four?

45. • The fact that GoF realized the power of the pattern language,
and wrote the first book does not limit the patterns to the 23.
• patterns is a very rich subject and not limitative to any list
provided by any single individual.
Are there more design patterns than the 23 of Gang oF four?

46. • There are plenty of other pattern repositories. As example,
there are Martin Fowler’s (more than 50) patterns of
enterprise application architecture, which are -despite their
name- also design patterns.
• There are several other repositories and books that describe
either general patterns or domain specific patterns, like for
example for the gaming industry.

47. ● You can try to invent one yourself as an
academic exercise, but as this answer already
suggests, the best way to uncover these
patterns is to find a bunch of seemingly
unrelated problems that have a common
solution. That common solution becomes the
design pattern.
How do we find new patterns?
● For example, the (Josh Bloch builder pattern (not to be
confused with the Gang of Four's builder pattern)) arose out
of the need for a readable way to initialize an object with a
large number of parameters, and was heavily influenced by
another design pattern, the fluent interface/API.

48. 1. MVC
2. Generic /regular Repository
3. Unit of work
4. Dependency Injection Pattern
5. Circuit Breaker
6. Command and Query Responsibility Segregation (CQRS)
7. Event Sourcing
8. Sidecar
9. Backend-for-Frontend
10. Strangler
Modern-Day Design Patterns
Some useful Design patterns for Graduation project

49. What is MVC
Model View Controller
Is it a pattern?
All architectural patterns are design patterns, but not all design
patterns are architectural. it's called architectural when its high
level pattern chosen in the application design phase.
MVC

50. An architectural pattern is a general, reusable solution to a
commonly occurring problem in software architecture within a
given context. Architectural patterns are similar to software
design pattern but have a broader scope.
Most Common
● MVC
● MVP
● MVVM
● CQRS
Architectural Pattern

51. Architecture
Vs
Architecture Pattern
VS
Design pattern

52. ● Software as a service
● MicroServices
● Onion Architecture
● Clean Architecture
● N-Tire (Layered Architecture)
● Serverless Architecture
● Event-Driven Architecture (Event Sourcing)
● Domain Driven Design (DDD)
Some Software Architectural

53. Design
Principles
samples

54. Anti Patterns

55. ● Anti-patterns are the opposite of best practice, which is a
solution that has been proven to be effective. They are often
used because they seem to work, but the larger context or
the long-term consequences are often not considered. They
can occur in :
● software design
● project management
● organizational behavior.
We should avoid Anti-Patterns
Anti-Patterns

56. common mistakes or poor practices when writing source code. That can lead
to problems like increased complexity and reduced maintainability.
● Spaghetti Code
● Boat anchor /Lava Flow
● Accidental Complexity
● God Object
● Hard Code / soft Code
● Magic (Numbers /Strings)
● Golden hammer
● Dead Code
● CarGo Cult Programming
● Single function exist point
Programming Anti-patterns

57. Anti Patterns (Cont.)