The document explains the strategy pattern, a design pattern in software that allows for the selection of an algorithm's behavior at runtime. It encapsulates a family of algorithms, making them interchangeable and suggesting their use in scenarios like calculating discounts in a shopping mall. Additionally, it emphasizes the open-closed principle, advocating for separable logic to enhance reusability and maintainability.

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Strategy Pattern

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Ganesh Kunwar
Sr. Software Engineer
Jyaasa Technologies

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What is Strategy Pattern?

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Ktm Butwal
Taxi Plan Taxi
Ktm.
Airport
Bhairahawa
Airport
Ktm Butwal
Taxi Bus
Kalanki
Ktm Butwal
Taxi Bus BusKalanki
Chitwan
Strategy 1
Strategy 2
Strategy 3

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Wikipedia Definition
the strategy pattern (also known as the policy pattern) is
a software design pattern that enables an algorithm's
behavior to be selected at runtime. The strategy pattern
● defines a family of algorithms,
● encapsulates each algorithm, and
● makes the algorithms interchangeable within that
family.

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When to Use?
Shopping Mall Example
- Accept customer detail
- Calculate bill amount
- Apply discount based on the day of week
- Monday - High discount (10%)
- Friday - Low discount (5%)

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Where does the discount logic reside?
Inside ShoppingMall class
Or
Outside ShoppingMall class

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Open closed principle
- software entities (classes, modules, functions, etc.) should be open
for extension, but closed for modification
- New discount logic may be applied in future
- Not reusable - Same discount strategy can be use in other shopping
mall

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Separate discount logic from ShoppingMall class

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Context Strategy

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=> grill = Grill.new(HotDog.new)
=> grill.grilling # => "Grilling the hot dogs!"
=> grill.food = Hamburger.new
=> grill.grilling # => "Grilling the hamburgers!"
=> grill.food = VeggiePatty.new
=> grill.grilling # => "Grilling the veggie patties!"

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References
- https://dockyard.com/blog/2013/07/25/design-patterns-strategy-pattern
- https://en.wikipedia.org/wiki/Strategy_pattern
- https://sourcemaking.com/design_patterns/strategy

16. Thank you!
Lets Discuss
github.com/glunwar
@gkunwar1
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