SOLID design principles for better team performance

SOLID design principles for better team performance Katerina Trajchevska, Bulgaria
PHP 2019

@ktrajchevska Katerina Trajchevska • Co-founder of Adeva, an exclusive developers’
network. • Software Engineer & Mozilla Tech Speaker • Consultant with startups and Fortune 500 @ktrajchevska

@ktrajchevska

@ktrajchevska SOLID design principles ー Write code that’s easy to
maintain. ー Easily extend the software with new functionality without breaking existing ones. ー Spend less time reading and more time writing code.

@ktrajchevska A class should have only one reason to change.
Single Responsibility Principle

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@ktrajchevska A class should be open for extension, but closed
for modification. Open/Closed Principle

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@ktrajchevska Don’t switch implementations, unless they give the same result.
Liskov Substitution Principle

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@ktrajchevska Don’t depend on methods you don’t use. Interface Segregation
Principle

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@ktrajchevska Depend on abstractions, not concretions. Dependency Inversion Principle

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@ktrajchevska Real Life SOLID Implementing developer profiles on Adeva’s Platform.

App\ZohoCandidate.php

App\Http\Controllers\CandidateController.php Controller knows too much and is open for modification.
Methods depend directly on the CRM storage and their naming conventions.

profile.blade.php View uses arrays that should be replaced with Collections
in future.

App\Http\Controllers\CandidateController.php

@ktrajchevska Changing storage from CRM to MySQL

@ktrajchevska 1. Adjust the edit method to work with MySQL

@ktrajchevska 2. Adjust the view to work with the new
implementation

@ktrajchevska 3. Adjust the update method to work with MySQL

@ktrajchevska 3. Adjust the update method to work with MySQL
(cont’d)

@ktrajchevska What does it take to change the storage? 1.
Add Eloquent models to use with MySQL. 2. Change controller dependencies from CRM class to Eloquent. 3. Use Eloquent instead of CRM to pull data for the view. 4. Switch all variables to the new naming convention. 5. Change the way we access data in the views. 6. Adjust the unit tests to work accordingly.

@ktrajchevska Time to switch: 30 days

@ktrajchevska How can we improve team performance by using SOLID
design principles?

@ktrajchevska 1. Segregate the interfaces.

@ktrajchevska App\Repositories\Interfaces\CandidateRepositoryInterface.php

@ktrajchevska 2. Don’t depend on concrete implementations.

@ktrajchevska App\Repositories\ZohoCandidateRepository.php

@ktrajchevska App\Http\Controllers\CandidateController.php

@ktrajchevska 3. Be mindful about what your program expects.

@ktrajchevska App\Crm\Candidate.php

@ktrajchevska profile.blade.php

@ktrajchevska 4. Separate the responsibilities.

@ktrajchevska

@ktrajchevska 5. Close the code for modification.

@ktrajchevska App\Providers\AppServiceProvider.php

@ktrajchevska Changing storage from CRM to MySQL: Take #2

@ktrajchevska

@ktrajchevska What does it take to switch the storage? 1.
Add Eloquent models to use with MySQL. 2. Create MysqlCandidateRepository that implements CandidateRepositoryInterface. 3. Change the binding for CandidateRepositoryInterface.

@ktrajchevska Time to switch: 5 days

@ktrajchevska Better team performance with SOLID ー Spending less time
reading code. ー Reducing time needed to extend the software. ー Reducing bugs by closing the core of the system. ー Improving productivity and reducing costs.

@ktrajchevska Is SOLID a “one size fits all” ?

@ktrajchevska ⚠ “Refactor away from SRP”

@ktrajchevska

@ktrajchevska Software Design Principles are your tools, not your goals.

@ktrajchevska Thank you!

SOLID design principles for better team perform...

SOLID design principles for better team performance

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