Strategy PatternShahriar Iqbal Chowdhury

Monjurul Habib

Code Name: Remington

http://www.facebook.com/groups/netter/

What is Strategy

A plan of action or policy designed to achieve a major or overall aim.

Why Need Pattern for Strategy

• The Strategy pattern is known as a behavioural pattern - it's used to manage algorithms, relationships and responsibilities between objects.

• The Strategy pattern is to be used where you want to choose the algorithm to use at runtime. A good use of the Strategy pattern would be saving files in different formats, running various sorting algorithms, or file compression

Strategy Pattern Says

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

OR

Why, When and How?

1. Allow a class to maintain a single purpose.

2. Switch statement

3. Adding a new implementation will cause a class file to be modified

4. Create a class for each strategy

5. Use a common interface for each strategy

Class Diagram

Pattern less Implementation

Context IStrategy

Concrete Strategy UPS Concrete Strategy USPS

WALL-E & Strategy

Strategy : Identify and Recycle Garbage

Strategy : Capable to Identify Object

Strategy : Identify Friend Strategy : Identify Girl Friend

Strategy : Identify New Hope For Mankind

Strategy @.Net Framework

• Array and ArrayList provide the capability to sort. Sort method will use the IComparable implementation for each element to handle the comparisons. Leaving the choice of comparison algorithm up to the user of the class like this is an example of the Strategy pattern.

• The use of a Predicate<T> delegate in the FindAll<T> method lets the caller use any method as a filter for the List<T> so long as it takes the appropriate object type and returns a Boolean.

That’s It!!