Writing Code That Lasts Forever (Droidcon NYC 2018)

Video: https://www.youtube.com/watch?v=YZstpc2939s
Code: https://github.com/swankjesse/maintainability

Developers are perpetually fighting yesterday’s code. We need to conquer our immortal fears and build programs that evolve gracefully.

In this talk we’ll:
🗿 Discuss code that anticipates the future
🗿 Determine when to adopt frameworks and when not to!
🗿 Defy object-oriented principles
🗿 Speak about how good English leads to good Kotlin
🗿 Learn who will leave a legacy of code, and who will leave because of legacy code

This talk addresses some timeless problems in software development. Attendees will gain a permanent understanding of how to write maintainable code.

Transcript

1. @jessewilson
   https://github.com/swankjesse/maintainability
   Writing Code
   That Lasts Forever
   

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2. Forever?
   

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3. • Maintainable: it’s ready for changes
   • Lasts Forever: it’s always ready for changes
   

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4. 1.0 1.1 1.2 1.3 1.4 1.5 1.6
   

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5. • There are many talks on maintainability – this one’s mine!
   • Not comprehensive
   • Ideas I think are important
   • Or that you might not have seen elsewhere
   7 + 7 Strategies
   

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6. Incentives
   STRATEGY #1
   

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7. 1. Figure out what you value
   2. Adjust incentives to reinforce those values
   

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8. • Don’t tell your team “write more tests”
   • Do find & remove barriers to writing tests
   

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9. Incremental Changes
   STRATEGY #2
   

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10. • Long-lived feature branches are bad!
    • Cherry-picking bug fixes to the release branch is bad
    • But releasing ½ of a feature is also bad!
    • Branch by abstraction: features can be turned on & off at runtime
    

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11. • master is always stable & shippable!
    • Per-feature betas
    • Decouple features & releases
    Why Branch By Abstraction?
    

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12. enum class BiometricAuth {
    NONE,
    FINGERPRINT,
    FINGERPRINT_OR_IRIS
    }
    

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13. interface Experimenter {
    fun > getBucket(experiment: KClass): T
    }
    

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14. class AuthScreen {
    @Inject lateinit var experimenter: Experimenter
    fun showBiometricAuth() {
    when (experimenter.getBucket(BiometricAuth::class)) {
    NONE -> skipBiometricAuth()
    FINGERPRINT -> showOldFingerprintAuth()
    FINGERPRINT_OR_IRIS -> showNewBiometricAuth()
    }
    }
    }
    

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15. Cash Debug Settings
    SendCashSuccessAnimation
    FADE
    WIPE
    SHREK_AND_FIONA
    ✔
    BiometricAuth
    NONE
    FINGERPRINT
    FINGERPRINT_OR_IRIS
    ✔
    NotificationSounds
    CHACHING
    BEEPS_AND_BOOPS
    BATMAN
    ✔
    15:17
    https://github.com/JakeWharton/u2020
    

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16. class AuthTest {
    @Inject lateinit var authScreen: AuthScreen
    @Inject lateinit var experimenter: FakeExperimenter
    @Test
    fun testNewBiometricAuth() {
    experimenter.setDefault(BiometricAuthentication.FINGERPRINT_OR_IRIS)
    ...
    }
    }
    

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17. Experiments Admin
    BiometricAuth
    NONE
    FINGERPRINT
    FINGERPRINT_OR_IRIS
    5
    95
    0
    SAVE
    SendCashSuccessAnimation
    FADE
    WIPE
    SHREK_AND_FIONA
    100
    0
    0
    SAVE
    https://admin.cashapp.square/experiments
    Experiments Admin
    

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18. • Deploy server + web code every
    day (or more frequently!)
    • Release mobile apps every 2
    weeks
    • Didn’t finish your feature in time?

    Another release is imminent!
    Release Trains
    

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19. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 1.11 1.12 1.13 1.14 1.15
    

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20. Learning Organizations
    STRATEGY #3
    

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21. • What features should we build?
    • How should they work?
    • What architecture should we use?
    • Which libraries should be adopt?
    Research & Development
    

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22. Perfect is Too Slow
    & Too Difficult
    

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23. • Try lots of things & see what works
    • Lower the cost of making mistakes
    • Tight feedback loops!
    Learning Means
    Making Mistakes
    

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24. Tools & Leverage
    STRATEGY #4
    

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25. • Example: gRPC
    • gRPC is an alternative to REST + JSON. It makes it faster and
    easier to define server endpoints
    Infrastructure Investments
    

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26. • Set up time:
    • REST: 0 hours (done)
    • gRPC: 80 hours
    • gRPC: 1 hour
    • Each new endpoint:
    • REST: 8 hours
    Number of Endpoints
    0
    4
    8
    12
    16
    Hours Invested
    0 16 32 48 64 80 96
    

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27. • If it takes 8 hours to add an
    endpoint, you’ll avoid adding
    endpoints when you need
    ’em
    • But if it only takes 1 hour
    you’ll add lots!
    Induced
    Demand!
    Number of Endpoints
    0
    4
    8
    12
    16
    Hours Invested
    0 16 32 48 64 80 96
    

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28. • Faster compiler? compile more!
    • Easier to write tests? test more!
    • Less severe errors? experiment more!
    

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29. • Slow code reviews? Fewer pull requests!
    Suppressed Demand
    

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30. Know Your Problem Domain
    STRATEGY #5
    

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31. • A good rule in general
    • But it’s even better if you know
    what you’re going to need!
    “You Ain’t Gonna Need It”
    YAGNI
    

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32. • Understanding the business is a superpower
    • Understanding the users’ needs is a superpower
    • You’ll be able to anticipate what You’re Gonna Need!
    

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33. Modeling
    STRATEGY #6
    

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34. • Bad models make everything difficult
    • Good models get out of your way
    • Models frame how you think about a problem
    • Changing models is a lot of work!
    Modeling is Critical
    

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35. • Users, your revenue team, your growth team, your legal team, etc.
    • Good models fit the stakeholders’ needs
    • And potentially recognize when they’re in conflict
    Stakeholders
    

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36. • Don’t ask male/female if you just want pronouns
    • If you collect a country without a particular purpose, you’re
    oversimplifying
    The World Isn’t Discrete
    

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37. Value Objects,
    Service Objects,
    & Glue
    STRATEGY #7
    

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38. • They’re data & can be encoded using JSON, SQL, etc.
    • Preferably immutable
    • Don’t do anything fancy: no I/O, no RxJava, no threading
    • Kotlin has built-in support via data classes
    • Might be simple enough to not need tests!
    • Examples: Paint, SendMoneyRequest, SettingsModel
    Value Objects
    

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39. • Do work & have side-effects (screen, file system, network)
    • May have injected dependencies of other service objects
    • May be worth splitting into interface + implementation
    • Test these!
    • Offer fake implementations too
    • Examples: Animator, SendMoneyService, HistoryDatabase
    Service Objects
    

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40. • The application’s plumbing
    • Awkward to test
    • Examples: activities, dagger modules, event listeners
    Glue
    

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41. • Architecture patterns (MVC, MVVM, etc.) specify how to combine
    these to create UIs
    • Virtual DOM is powerful because it uses value objects for views
    • Primary benefit of React/Native
    • And it’s why I’m excited about Domic
    3 Kinds of Objects & Android
    https://github.com/lyft/domic
    

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42. English, then Code
    STRATEGY #8
    

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43. Writing is thinking
    Why is writing so hard?
    

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44. • Tell you what is scope and what’s out of
    scope
    • android.graphics.Paint is a bad name
    because it includes too much: text alignment,
    stroke width, and text measurement
    • Use a thesaurus!
    Naming Matters
    

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45. Shipley’s Law
    STRATEGY #9
    

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46. Less code is better code
    ∴ No code is the best code
    Wil Shipley
    

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47. The Type System
    Works for You
    STRATEGY #10
    

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48. • JavaScript programmers: types are a lot of work for what you get
    • Java programmers: I need separate types for
    OnItemClickListener and OnItemLongClickListener
    

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49. interface GeoLocationService {
    fun latest(): GeoLocation
    }
    

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50. interface GeoLocationService {
    fun latest(): GeoLocation
    /**
    * For testing only. This doesn't actually teleport the device
    * to a new location. It merely overrides what [latest] returns.
    */
    fun teleport(newLocation: GeoLocation)
    }
    

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51. Organize By Feature
    STRATEGY #11
    

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52. Organizing by Technology
    com.roundsapp
    models
    persistence
    services
    viewmodels
    views
    fragments
    activities
    • Redundant
    • For example, your views already
    have “View” in the class name
    

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53. Organizing by Feature
    com.roundsapp
    gamesummary
    scorekeeping
    gamelist
    creategame
    • Simplifies extracting features into
    submodules
    • Rewriting a feature? Start by copy-
    pasting its package!
    • Retiring a feature? Easy to find
    what to delete
    

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54. Building Blocks
    STRATEGY #12
    

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55. Dimetrodon
    Diplodocus
    Triceratops
    Stegosaurus
    Velociraptor
    Brachiosaurus
    Ankylosaurus
    Edmontosaurus
    Pterodactyl
    Dinosaur Extinct!
    15:24
    

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56. Stegosaurus
    Diplodocus
    Velociraptor
    Triceratops
    Brachiosaurus
    Ankylosaurus
    Edmontosaurus
    Pterodactyl
    Tyrannosaurus
    Dinosaur Extinct! UNDO
    15:24
    

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57. Toast.makeText(getActivity(), "Dinosaur Extinct!", Toast.LENGTH_LONG).show()
    

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58. public class UndoToast {
    public interface OnDismissListener {
    void onDismiss(View view, Parcelable token);
    }
    private final Context mContext;
    private final View mView;
    private final TextView mTextView;
    private Style mStyle;
    private OnDismissListener mOnDismissListener;
    public UndoToast(@NonNull Context context) {
    this.mContext = context;
    this.mStyle = new Style();
    this.mStyle.type = Style.TYPE_STANDARD;
    final LayoutInflater layoutInflater = (LayoutInflater) context
    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    this.mView = onCreateView(context, layoutInflater, Style.TYPE_STANDARD);
    this.mTextView = (TextView) this.mView.findViewById(R.id.message);
    }
    protected UndoToast(@NonNull Context context, @Style.Type int type) {
    this.mContext = context;
    this.mStyle = new Style();
    this.mStyle.type = type;
    final LayoutInflater layoutInflater = (LayoutInflater) context
    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    this.mView = onCreateView(context, layoutInflater, type);
    this.mTextView = (TextView) this.mView.findViewById(R.id.message);
    }
    protected UndoToast(@NonNull Context context, @NonNull Style style, @Style.Type int type) {
    this.mContext = context;
    this.mStyle = style;
    this.mStyle.type = type;
    final LayoutInflater layoutInflater = (LayoutInflater) context
    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    this.mView = onCreateView(context, layoutInflater, type);
    this.mTextView = (TextView) this.mView.findViewById(R.id.message);
    }
    protected UndoToast(@NonNull Context context, @NonNull Style style, @Style.Type int type, @IdRes int viewGroupID) {
    this.mContext = context;
    this.mStyle = style;
    this.mStyle.type = type;
    // TYPE_BUTTON styles are the only ones that look different from the styles set by the Style() constructor
    if (type == Style.TYPE_BUTTON) {
    this.mStyle.yOffset = BackgroundUtils.convertToDIP(24);
    this.mStyle.width = FrameLayout.LayoutParams.MATCH_PARENT;
    }
    final LayoutInflater layoutInflater = (LayoutInflater) context
    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    this.mView = onCreateView(context, layoutInflater, type);
    this.mTextView = (TextView) this.mView.findViewById(R.id.message);
    

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59. • An inventory of classes that can be composed to build things
    • Rearrange ’em to solve new problems
    Maintainable APIs work like Lego
    

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60. val request = Request.Builder()
    .url("https://lego.com/")
    .build()
    val call = client.newCall(request)
    call.execute().use {
    println(it.body().string())
    }
    1
    2
    3
    404
    flickr.com/photos/blakespot
    

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61. Policy & Precedence
    STRATEGY #14
    

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62. • Code that implements product decisions
    • Can be visible: character limit of a Tweet
    • Or hidden: you can’t send the same tweet twice
    • Or implicit: the call times out after 30 seconds and is retried twice
    Policy
    

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63. • No size limit on your profile photo? The universe will impose its
    own limit and you will be sad
    No Policy is a Policy
    

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64. • In school we’re taught to be avoid magic numbers
    • In practice: don’t bury policy
    Maintainable Policies
    

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65. @Inject @Named("base") lateinit var baseUrl: HttpUrl
    @Inject lateinit var client: OkHttpClient
    fun upload(file: File, endpoint: String): Boolean {
    val options = BitmapFactory.Options()
    options.inJustDecodeBounds = true
    BitmapFactory.decodeFile(file.path!!, options)
    require(options.outWidth < 5000 && options.outHeight < 5000)
    val request = Request.Builder()
    .url(baseUrl.resolve(endpoint)!!)
    .post(RequestBody.create(MediaType.parse(options.outMimeType), file))
    .build()
    // Extend timeouts for large uploads. See IMAGINARY-3211.
    val uploadClient = client.newBuilder()
    .writeTimeout(30, TimeUnit.SECONDS)
    .readTimeout(30, TimeUnit.SECONDS)
    .build()
    val call = uploadClient.newCall(request)
    ...
    

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66. class ImageUploadPolicy {
    fun checkBounds(width: Int, height: Int) {
    require(width < 5000 && height < 5000)
    }
    }
    

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67. require(options.outWidth < 5000 && options.outHeight < 5000)
    @Inject @Named("base") lateinit var baseUrl: HttpUrl
    @Inject lateinit var client: OkHttpClient
    fun upload(file: File, endpoint: String): Boolean {
    val options = BitmapFactory.Options()
    options.inJustDecodeBounds = true
    BitmapFactory.decodeFile(file.path!!, options)
    val request = Request.Builder()
    .url(baseUrl.resolve(endpoint)!!)
    .post(RequestBody.create(MediaType.parse(options.outMimeType), file))
    .build()
    // Extend timeouts for large uploads. See IMAGINARY-3211.
    val uploadClient = client.newBuilder()
    .writeTimeout(30, TimeUnit.SECONDS)
    .readTimeout(30, TimeUnit.SECONDS)
    .build()
    ...
    

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68. require(options.outWidth < 5000 && options.outHeight < 5000)
    @Inject @Named("base") lateinit var baseUrl: HttpUrl
    @Inject lateinit var client: OkHttpClient
    fun upload(file: File, endpoint: String): Boolean {
    val options = BitmapFactory.Options()
    options.inJustDecodeBounds = true
    BitmapFactory.decodeFile(file.path!!, options)
    val request = Request.Builder()
    .url(baseUrl.resolve(endpoint)!!)
    .post(RequestBody.create(MediaType.parse(options.outMimeType), file))
    .build()
    // Extend timeouts for large uploads. See IMAGINARY-3211.
    val uploadClient = client.newBuilder()
    .writeTimeout(30, TimeUnit.SECONDS)
    .readTimeout(30, TimeUnit.SECONDS)
    .build()
    ...
    @Inject lateinit var imageUploadPolicy: ImageUploadPolicy
    

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69. @Inject @Named("base") lateinit var baseUrl: HttpUrl
    @Inject lateinit var client: OkHttpClient
    fun upload(file: File, endpoint: String): Boolean {
    val options = BitmapFactory.Options()
    options.inJustDecodeBounds = true
    BitmapFactory.decodeFile(file.path!!, options)
    val request = Request.Builder()
    .url(baseUrl.resolve(endpoint)!!)
    .post(RequestBody.create(MediaType.parse(options.outMimeType), file))
    .build()
    // Extend timeouts for large uploads. See IMAGINARY-3211.
    val uploadClient = client.newBuilder()
    .writeTimeout(30, TimeUnit.SECONDS)
    .readTimeout(30, TimeUnit.SECONDS)
    .build()
    ...
    @Inject lateinit var imageUploadPolicy: ImageUploadPolicy
    

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70. @Inject @Named("base") lateinit var baseUrl: HttpUrl
    @Inject lateinit var client: OkHttpClient
    fun upload(file: File, endpoint: String): Boolean {
    val options = BitmapFactory.Options()
    options.inJustDecodeBounds = true
    BitmapFactory.decodeFile(file.path!!, options)
    val request = Request.Builder()
    .url(baseUrl.resolve(endpoint)!!)
    .post(RequestBody.create(MediaType.parse(options.outMimeType), file))
    .build()
    // Extend timeouts for large uploads. See IMAGINARY-3211.
    val uploadClient = client.newBuilder()
    .writeTimeout(30, TimeUnit.SECONDS)
    .readTimeout(30, TimeUnit.SECONDS)
    .build()
    ...
    @Inject lateinit var imageUploadPolicy: ImageUploadPolicy
    imageUploadPolicy.checkBounds(options.outWidth, options.outHeight)
    

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71. class NetworkingModule : AbstractModule() {
    /** Extend timeouts for large uploads. See IMAGINARY-3211. */
    @Provides @Named("image_uploads")
    fun provideImageUploadsHttpClient(client: OkHttpClient): OkHttpClient {
    return client.newBuilder()
    .writeTimeout(30, TimeUnit.SECONDS)
    .readTimeout(30, TimeUnit.SECONDS)
    .build()
    }
    ...
    }
    

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72. @Inject @Named("base") lateinit var baseUrl: HttpUrl
    @Inject
    fun upload(file: File, endpoint: String): Boolean {
    val options = BitmapFactory.Options()
    options.inJustDecodeBounds = true
    BitmapFactory.decodeFile(file.path!!, options)
    @Inject lateinit var imageUploadPolicy: ImageUploadPolicy
    imageUploadPolicy.checkBounds(options.outWidth, options.outHeight)
    lateinit var client: OkHttpClient
    val request = Request.Builder()
    .url(baseUrl.resolve(endpoint)!!)
    .post(RequestBody.create(MediaType.parse(options.outMimeType), file))
    .build()
    // Extend timeouts for large uploads. See IMAGINARY-3211.
    val uploadClient = client.newBuilder()
    .writeTimeout(30, TimeUnit.SECONDS)
    .readTimeout(30, TimeUnit.SECONDS)
    .build()
    ...
    val call = .newCall(request)
    uploadClient
    

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73. @Named("image_uploads")
    @Inject @Named("base") lateinit var baseUrl: HttpUrl
    @Inject
    fun upload(file: File, endpoint: String): Boolean {
    val options = BitmapFactory.Options()
    options.inJustDecodeBounds = true
    BitmapFactory.decodeFile(file.path!!, options)
    @Inject lateinit var imageUploadPolicy: ImageUploadPolicy
    imageUploadPolicy.checkBounds(options.outWidth, options.outHeight)
    val request = Request.Builder()
    .url(baseUrl.resolve(endpoint)!!)
    .post(RequestBody.create(MediaType.parse(options.outMimeType), file))
    .build()
    // Extend timeouts for large uploads. See IMAGINARY-3211.
    val uploadClient = client.newBuilder()
    .writeTimeout(30, TimeUnit.SECONDS)
    .readTimeout(30, TimeUnit.SECONDS)
    .build()
    ...
    val call = .newCall(request)
    client
    lateinit var client: OkHttpClient
    

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74. @Named("image_uploads")
    @Inject @Named("base") lateinit var baseUrl: HttpUrl
    @Inject
    fun upload(file: File, endpoint: String): Boolean {
    val options = BitmapFactory.Options()
    options.inJustDecodeBounds = true
    BitmapFactory.decodeFile(file.path!!, options)
    @Inject lateinit var imageUploadPolicy: ImageUploadPolicy
    imageUploadPolicy.checkBounds(options.outWidth, options.outHeight)
    val request = Request.Builder()
    .url(baseUrl.resolve(endpoint)!!)
    .post(RequestBody.create(MediaType.parse(options.outMimeType), file))
    .build()
    ...
    val call = .newCall(request)
    client
    lateinit var client: OkHttpClient
    

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75. • Many systems all trying to make the
    same decisions
    • Example: Android themes
    Precedence I wrote some new
    features for you!
    Come again?
    BUT THE CODE IS
    ALREADY WRITTEN!
    I can’t hear you
    15:33
    

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76. • Difficult to predict what will happen
    • Avoid ’em
    Precedence Rules
    are Clumsy!
    I wrote some new
    features for you!
    Come again?
    BUT THE CODE IS
    ALREADY WRITTEN!
    I can’t hear you
    15:33
    

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77. Finish Transitions
    Get Cake
    STRATEGY #15
    

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79. View Slide

80. 2009
    Apache HTTP client
    

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81. 2009
    Apache HTTP client org.json
    

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82. 2009
    Apache HTTP client org.json AsyncTask
    

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83. 2010
    Apache HTTP client org.json AsyncTask
    

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84. 2010
    Apache HTTP client org.json AsyncTask
    Gson
    

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85. Apache HTTP client org.json AsyncTask
    HttpURLConnection Gson
    2011
    

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86. Apache HTTP client org.json AsyncTask
    HttpURLConnection Gson
    Volley
    Callbacks
    2013
    

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87. Apache HTTP client org.json AsyncTask
    HttpURLConnection Gson
    Volley
    Retrofit Callbacks
    RxJava
    OkHttp 2
    2014
    

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88. Apache HTTP client org.json AsyncTask
    HttpURLConnection Gson
    Volley
    Retrofit
    Retrofit 2
    Callbacks
    RxJava
    OkHttp 3
    OkHttp 2
    2015
    

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89. Apache HTTP client org.json AsyncTask
    HttpURLConnection Gson
    Volley
    Retrofit
    Retrofit 2
    Callbacks
    RxJava
    OkHttp 3
    Moshi
    OkHttp 2
    2016
    

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90. Apache HTTP client org.json AsyncTask
    HttpURLConnection Gson
    Volley
    Retrofit
    Retrofit 2
    Callbacks
    RxJava
    OkHttp 3
    Moshi
    OkHttp 2
    Moshi-Kotlin
    2018
    

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91. Apache HTTP client org.json AsyncTask
    HttpURLConnection Gson
    Volley
    Retrofit
    Retrofit 2
    Callbacks
    RxJava
    OkHttp 3
    Moshi
    OkHttp 2
    Moshi-Kotlin
    

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92. Retrofit 2 RxJava
    OkHttp 3 Moshi-Kotlin
    

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93. • Android SDK, build tools, server APIs, libraries
    • In-flight transitions are friction!
    Life in Transition
    

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94. • Plan to celebrate with your team when you finish a transition:

    cake, or team lunch, t-shirts, stickers, or Vegas
    • Keep your eyes on the prize when coding is a grind
    

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95. Takeaways
    FIN
    

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96. 1. People respond to incentives
    2. Branch by abstraction
    3. Build learning into your process
    4. Infrastructure induces demand
    5. Embrace your problem domain
    6. Understand stakeholders
    7. Minimize glue
    8. Writing is thinking
    9. Less code is better
    10. The type system is just a tool
    11. Organize by feature
    12. Create building blocks
    14. Policy good; precedence bad
    15. Eat Cake
    

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97. @jessewilson
    https://github.com/swankjesse/maintainability
    Thanks
    

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