Clean Architecture - Speaker Deck

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Software Engineers | GDP Labs KASKUS Chat Android - Lessons Learned

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The big names

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3 / 67 https://8thlight.com/blog/uncle-bob/2012/08/13/the-clean-architecture.html

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4 / 67 Alistair Cockburn

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5 / 67 Jeffrey Pallermo

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6 / 67 James Coplien, and Trygve Reenskaug Ivar Jacobson

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7 / 67 Robert C. Martin https://8thlight.com/blog/uncle-bob/2012/08/13/the-clean-architecture.html

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8 / 67 ❏ Independent of any external agencies, e.g. frameworks, UI, database. ❏ Testable The Characteristics

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9 / 67 O’Reilly Software Architecture Conference 2017

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10 / 67 What’s the difference? BLOCK DIAGRAM DEPENDENCY DIAGRAM

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Software was invented to be soft

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12 / 67 Software was invented to be “soft” Soft → Easy to change Hard to change → Hardware How do we make software soft? By leaving as many options open as possible, for as long as possible. - Robert C. Martin

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13 / 67 Keeping Options Open I/O Devices Databases Web systems Desktop systems Communication protocol Monolithic / Microservices Drivers Servers Frameworks UI Mediums

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14 / 67 ❏ Single Responsibility Principle ❏ Open-Closed Principle ❏ Liskov Substitution Principle ❏ Interface Segregation Principle ❏ Dependency Inversion Principle SOLID Principle

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Why is it important?

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16 / 67 Polymorphism - copy program same copy program different I/O devices

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17 / 67 Polymorphism - copy program COPY CONSOLE READER CONSOLE WRITER READER WRITER : interface Punch Cards Magnetic Tapes Floppy Disks https://sherpasoftware.com/blog/the-evolution-of-data-storage/ Compact Disks Flash Drives Cloud

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18 / 67 The power of polymorphism Martin, Robert C. 2017. Clean Architecture - A Craftsman's Guide to Software Structure and Design. Prentice Hall. Ch. 5

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19 / 67 The power of polymorphism Martin, Robert C. 2017. Clean Architecture - A Craftsman's Guide to Software Structure and Design. Prentice Hall. Ch. 5

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20 / 67 Benefits Independent Deployability Independent Developability Martin, Robert C. 2017. Clean Architecture - A Craftsman's Guide to Software Structure and Design. Prentice Hall. Ch. 5

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21 / 67 https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720005243.pdf https://www.hq.nasa.gov/alsj/S66-05120.jpg ...on Apollo spacecraft design INDEPENDENT DEVELOPABILITY!

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What’s the difference(s)?

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29 / 67 Inversion of Control

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32 / 67 Martin Fowler Inversion of Control is a common phenomenon that you come across when extending frameworks. Indeed it's often seen as a defining characteristic of a framework. - Martin Fowler | https://martinfowler.com/bliki/InversionOfControl.html

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33 / 67 Martin Fowler As a result I think we need a more specific name for this pattern. Inversion of Control is too generic a term, and thus people find it confusing. As a result with a lot of discussion with various IoC advocates we settled on the name Dependency Injection. - Martin Fowler | https://martinfowler.com/articles/injection.html

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Idealistic vs Pragmatic

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35 / 67 Idealistic vs Pragmatic IDEALISTIC PRAGMATIC

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36 / 67 BEFORE AFTER Dependency Diagram

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37 / 67 https://github.com/android10/Android-CleanArchitecture DEPENDENCY DIAGRAM BLOCK DIAGRAM

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38 / 67 Dependency Diagram 1st Iteration data domain presentation data domain presentation WHAT WE THINK WE HAVE (...and wrong) REALITY (even worse)

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39 / 67 Dependency Diagram 2nd Iteration data domain presentation THE CORRECT ONE

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40 / 67 Mapping to Clean Architecture data domain presentation SMACK ORMLite Android Fragment

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41 / 67 Clean Architecture Independent Deployability Independent Developability Easily swap/upgrade third parties

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42 / 67 Easily swap/upgrade third parties Upgrade SMACK 4.1.6 to 4.1.8 (with breaking changes) Minimum usages

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How components communicate

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44 / 67 Flow of Control

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One step further from Library vs Framework

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50 / 67 Dependency Diagram 3rd Iteration domain data presentation sdk sdk-ui app-1 app-2 Third Party App Android Fragment SMACK ORMLite

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51 / 67 Dependency Diagram 3rd Iteration domain data presentation sdk sdk-ui app-1 app-2 Third Party App SDK Boundary Core Boundary SMACK ORMLite

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52 / 67 Dependency Diagram 3rd Iteration Core sdk app-1 app-2 Third Party App SDK Boundary Core Boundary SMACK ORMLite

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...or shall you? (BGM: Marry You - Bruno Mars)

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54 / 67 Idealistic vs Pragmatic build.gradle (domain) data domain presentation rxjava !

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Overkill?

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57 / 67 Concrete - data package - many imports Interface - domain package - few imports

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Bottom-up or top-down

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59 / 67 Designing Interfaces 1. Create concrete class first 2. Adjust the interface 3. Unit test 1. Create interface based on req 2. Unit test 3. Implement concrete class Bottom-Up Top-Down 4. Refactor 0. Read Open-Source Code

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60 / 67 Designing Interfaces “Client should not be forced to depend upon interface that they do not use”

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...with (things that are not) the Kardashians

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62 / 67 Keeping up with (things that are not) the Kardashians https://developer.android.com/jetpack/ RxJava 1.0 18 Nov 2014 (support ends 31 Mar 2018) RxJava 2.0 29 Oct 2016

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Recapping...

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64 / 67 ❏ {Hexagonal, Onion, DCE, BCE, Clean} Architecture ❏ Block vs Dependency Diagram ❏ Software was invented to be soft ❏ Dependency Inversion / Inversion of Control / DI ❏ Independent {Deployability, Developability} ❏ Easily swap/upgrade third parties ❏ Flow of Control ❏ Library vs Framework ❏ SDK!

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65 / 67 ❏ Idealistic vs Pragmatic ❏ One Interface One Implementation ❏ Designing Interfaces ❏ Read open-source code ❏ Bottom-Up vs Top-Down ❏ Interface Segregation Principle ❏ Keep up with (things that are not) the Kardashians ❏ What we learn/decide today will be obsolete tomorrow

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66 / 67 Use common sense Every system is unique Every system is different

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Questions/Comments? Let’s discuss! PING Android team [email protected]

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