From Good to SOLID - Speaker Deck

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Katerina Trajchevska From Good to SOLID Architecture

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Katerina Trajchevska ● Senior Software Engineer & co-founder of Adeva ● Remote Work Advocate ● Community Volunteer ● Consultant with startups and Fortune 500 companies Software Engineer and co-founder of Adeva

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@ktrajchevska The state of software development Cutting costs by sacrificing good software architecture.

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@ktrajchevska SOLID Design Principles ● Encourage writing code that is: ○ Easier to read and understand ○ Easier to maintain ○ Easier to extend ● Introduced by Robert Martin (Uncle Bob), named by Michael Feathers.

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Single Responsibility Principle A class should have one, and only one, reason to change.

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@ktrajchevska Single Responsibility Principle ● A class should only do one thing. ● Find one responsibility and move everything else out of the class. ● Very precise names for many small classes > generic names for large classes.

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Open/Closed Principle An entity should be open for extension, but closed for modification.

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@ktrajchevska Open/Closed Principle ● Extend functionality by adding new code instead of changing existing one. ● Easily extend the system; never break it. ● Example: Open Source library

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Liskov Substitution Principle Let φ(x) be a property provable about objects x of type T. Then φ(y) should be true for objects y of type S where S is a subtype of T.

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@ktrajchevska Liskov Substitution Principle ● Any class should be able to substitute its parent class without breaking the program. ● Every class that implements an interface, must be able to substitute any other class that implements the same interface without breaking the program. ● Every part of the code should get the expected result.

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Returns Illuminate\Support\Collection

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Returns array

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Returns Illuminate\Support\Collection

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Interface Segregation Principle No client should be forced to depend on methods it does not use.

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@ktrajchevska Interface Segregation Principle ● A client should never be forced to depend on methods it doesn't use. ● Changing one method in a class shouldn’t affect classes that don’t depend on it. ● Replace a large interface with many small, specific interfaces.

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Illuminate\Database\ Eloquent\Model: 1600+ lines of code

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Dependency Inversion Principle High-level modules should not depend on low-level modules. Both should depend on abstractions.

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@ktrajchevska Dependency Inversion Principle ● Never depend on anything concrete, only depend on abstractions. ● High level modules should not depend directly on low level modules. ● Able to change an implementation easily without altering the high level code.

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@ktrajchevska The results of SOLID Cutting costs by implementing good software architecture.

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@ktrajchevska ⚠ Words of caution ● SOLID design principles are principles, not rules. ● Know your trade-offs and use common sense when applying SOLID. ● Avoid over-fragmenting your code. ● Don’t try to achieve SOLID, use SOLID to achieve better developer experience.

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@ktrajchevska Final Thoughts ● SOLID helps you achieve code that’s easy to maintain, extend and understand. ● Spend more time writing and less time reading code. ● Always know your trade-offs and use common sense.