Design Pattern:: Template Method

The template method pattern is a behavioral design pattern that defines the program skeleton of an algorithm in an operation, deferring some steps to subclasses.

1. Design Pattern::Template Method
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2. Hello !
I am Neha Suwal
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Associate Software Engineer
Jyaasa Technologies

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Gang of Four Definition:

“Define a skeleton of an algorithm in an operation,
deferring some steps to subclasses. It lets subclasses
redefine certain steps of an algorithm without changing its
subclasses.”


Template Method

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That means, instead of having a huge if/switch/ case statement
somewhere to control what happens, Template Method lets object itself
determine what happens by using a method that all siblings inherit but
implement in their own way.
What does that mean?

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Structure

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●`template_method` calls `step_one` method, `step_two` method and
`step_three` method
●`step_two` is a hook method. I.e It is declared in base class and
then defined in subclasses

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Where to use?
●A class has more than one method that each contains an
if/switch/case statement with 3 or more possibilities.
●A class which has an if/switch/case statement that can have new
possibilities as conditions in the future.

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Example
OUTPUT:

MOO MOO
OINK OINK
QUACK QUACK

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Example
OUTPUT:

MOO MOO

uninitialized constant
Animal::NotImplemented
Exception (NameError)

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●No code duplication
●Since uses inheritance code is reused
●Lets subclasses decide how to implement steps in an algorithm.
Advantage

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●Understanding the sequence of flow
●Problem in maintenance
Disadvantage

12. Thank you!
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