Refactoring to Kotlin - Kotlin/Everywhere

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Refactoring to Kotlin Wajahat Karim Moving Big Old Java Codebase to New Awesome Kotlin WajahatKarim

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I am Wajahat Karim And I work at Contour Software. Hey There! Coding 8+ Years Experienced Android Developer Writing Authored 2 Worldwide Published Books Passion Open Source Contributor (many Android libraries) Community AndroidPub, FlutterPub, Articles, and Talks

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This is a story of...

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Messy Code Deprecated Libraries Frustrated Developers Not-so-happy Clients And Project X

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An Uber-like app for businesses (B2B) 73+ screens and counting 6+ different apps for each customer with own colors, server, features 400+ classes (including Activity, Views, Models, POJOs) Existing codebase to work upon - Code modiﬁcation takes double time. Project X

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What We Expected Modern APIs & Frameworks Some good architecture like MVP, MVVM etc. Well organized & commented code Unit & Instrumentation Tests

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What We Got Modern APIs & Frameworks - 2010 codebase never upgraded in years Some good architecture like MVP, MVVM etc. - Everything is in one BIG class. Well organized & commented code - Who has time for it? Unit & Instrumentation Tests - Sorry? What’s that? Never heard of it before.

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Old Code Architecture

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Let’s convert it Kotlin... CTRL + SHIFT + K

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No content

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New Code Architecture

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Refactor vs Rewrite No disturbance in existing features New features & bug ﬁxes Tight deadlines & less time Too big risk to handle Refactoring

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What We Did 1. Move all network code to Network Repository 2. Move all local persistence code to Local Repository 3. Move everything except UI, Navigation, & Business Logic to Common / Utils 4. Create separate Activity/Fragment from big multiple-screen classes 5. Integrate Kotlin & MVVM Core classes 6. Move Business Logic to ViewModel

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1. Unit & Instrumentation Testing 2. CI/CD Automation 3. Integrate Room database 4. Integrate Retroﬁt + Coroutines What’s Next

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Show’em the code!

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Kotlin Extensions = ❤ https://wajahatkarim.com/2019/03/-launching-activities-in-easier-way-using-kotlin-extensions-

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Domain Speciﬁc Language (DSL) Java Kotlin with DSL Builder https://android.jlelse.eu/domain-specific-language-dsl-using-kotlin-with-retrofit-example-9be5ef65a4fb

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@JVMStatic Kotlin Without @JVMStatic in Java With @JVMStatic in Java

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https://wajahatkarim.com [email protected] github.com/wajahatkarim3 @WajahatKarim Any Questions? medium.com/@wajahatkarim3