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

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