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Design Patterns in Object Oriented Design
In this presentation I discuss about Design Patterns found in Object Oriented Programming. Mainly there are 3 types of design patterns. Creational Design Patterns - About the creation of objects Structural Design Patterns - About Putting Objects together Behavioral Design Patterns - About how objects interact with each other
Design Patterns in Object Oriented Design
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- 3. Guess the object It'sa hefty land vehicle, typically with multiple axles and large, robust tires. Its defining feature is a separate articulated section at the rear, designed for carrying substantial loads. This trailing portion often appears as a large box or open platform
- 4. Creational Patterns How objectsget created
- 5. Abstract Factory Light ThemeDark Theme
- 6. Abstract Factory ● Create setsor families of related objects
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- 9. Builder Pattern ● For objectsthat need many options for creation ● Avoid creating large constructors ● Fine tuned object creation
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- 12. Factory Method ● Let aclass defer the instantiation of an object to it’s subclass ● Useful if multiple subclasses need similar objects with slightly different features ● Decouples the creation of an object from its usage
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- 15. Prototype ● Create new objectsby cloning existing ones ● Performant ● Avoid sub classing
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- 18. Singleton ● Ensure a classhas only one instance ● Provide single global access
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- 22. Adapter ● When a targetinterface doesn’t match the client interface ● Sits in the middle of a target and client
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- 24. Bridge ● Decoupling abstraction fromimplementation ● Two separate class hierarchies – Abstraction : What – Implementation : How ● Useful when abstraction and implementation wants to change independently
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- 27. Composite ● Tree structures ● Perform sameoperation on single leaf or entire branch
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- 31. Decorator ● Dynamically add responsibilitiesand behaviours to objects ● Decorator takes an instance of an interface or another decorator in the constructor ● When a method is called it does something and pass the call to wrapped object ● External users still call the interface, doesn’t know how many layers it has
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- 33. Façade ● Provide a singleunified simple interface for a larger complex subsystem ● Client depend only on the Façade
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- 36. Flyweight ● Support huge numberof fine tuned objects ● Separate state into two types – Intrinsic state : Invariant / Sharable – Extrinsic state : Variable / Depend on context ● One flyweight object carrying intrinsic state shared by all objects
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- 39. Proxy ● Acts as aplaceholder for another object ● Controls access and Intercept calls ● Has the same interface as the target
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- 41. Behavioural Patterns How objectsinteract
- 42. Chain of Responsibility Customer Customer Care Technical Tier1 Technical Tier 2 Management
- 43. Chain of Responsibility ● Whena lot of receivers can solve a request, but sender doesn’t have to know which one to send ● Create a chain of receiver objects
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- 46. Command ● Separate request foran action from implementation ● Wraps request into command object
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- 49. Interpreter ● Create grammar forlanguage and understand it ● Expression class hierarchy ● Recursive
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- 51. Iterator ● Iterate without knowingimplementation
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- 53. Mediator ● Avoid direct communication ● Allcalls go through mediator ● Promote loose coupling
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- 57. Memento ● Capture object’s internalstate without breaking encapsulation ● Knows how to create and restore objects
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- 60. Observer ● Manage one tomany dependencies ● When state changes, all observers get notified ● Observers register with subject, subject keeps a list of observers
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- 63. State Pattern ● When objectsbehaviour changes according to internal state ● Avoid using if statements ● Encapsulate behaviours into state objects
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- 66. Strategy Pattern ● When thereare multiple strategies to do some task ● Encapsulate all algorithms into separate strategy objects ● Open for extension, closed for modification
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- 69. Template Method ● Write atemplate algorithm in a base class, subclasses override it ● A sequence of methods that individually can be overridden
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- 72. Visitor ● Perform operations onobjects without changing their classes ● Visitor has .accept() method ● Element opens the door, visitor comes in and does the work according to type.
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