DesignPatterns

Design Patterns and Design Principles with their best practices and description

Keywords for Memorization

Strategy:

Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from the clients that use it.

• family
• interchangable
• vary independenty

Factory:

Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses.

• family
• interchangable
• vary independenty

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Visitor: O-P-E-S

Represent an operation to be performed on the elements of an object structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates.

• represent an Operation
• Performed on an
• Elements of object
• in a Structure

Composite: C-T-P-T

Compose objects into tree structures to represent whole-part hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly.

• Compose
• Tree structure
• represent Part-whole hierarchies
• Treat individual objects and compositions

Iterator: E-A-S-E

Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.

• access Element
• Aggregate object
• Squencially
• wihtout Exposing

Proxy: S-P-A

Provide a surrogate or placeholder for another object to control access to it.

• Surrogate
• Placeholder
• control Access

Visitor

Good Video Materials from YT

• from Derek Banas - THE BEST!

Difference between

• Strategy vs State

• Proxy vs Decorator vs Adapter vs Facade

• Decorator vs Adapter

Decorator DP	Composite DP
add new behaviour	part-whole hierarchy
linear structure	tree structure
one dimensional	two dimensional
only one node	one or more nodes

wrapper patterns

• Beautifully put statement from SO