Replacing Conditionals With

Polymorphism@gpespn

“Any fool can write code that a computer can understand.

Good programmers write code that humans can understand.”

-- Martin Fowler

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But why? • Easier to read • Maintainability • Extensibility • Isolation of change • Easier to test

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B+

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C-

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New Feature! Guest sessions

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F-

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I just want to send a message

to an object

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-Woof!

-Meow!

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Polymorphism

tell don't ask

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still have conditional!

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Create a high level abstract

class

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Abstract Subclass Subclass

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Polymorphism

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Whats the catch? • Parallel interfaces • Design patterns that are confusing to those unfamiliar to them

• New words/vocabulary into application. LOC went up! • Increased big picture complexity in exchange for macro clarity

• Too many Objects

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Questions?