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Can you read my code?

Can you read my code?

We will never be able to write a piece of code and not looking at it ever again 'cos "It works!".
When we collaborate with other people is critical to contribute with readable and maintainable code.
Kotlin offer a very concise syntax, but that's not enough, so in this talk I will go through my development habits and Kotlin tricks to increase readability.
by Ivan Morgillo
presented on December 12, 2017 @yelp

Kotlin User Group Hamburg

December 12, 2017
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  1. COMMENTS COMMENT THE WHY NOT THE WHAT "foo() looks like

    this because it turned out all the other 15 solutions we tried sucked”
  2. COMMENTS COMMENT MAGIC CONSTANTS val NUM_THREAD = 8 // My

    desk legs * 2 val MAGIC_CONSTANT = 42 // The Answer
  3. COMMENTS USE COMMON MARKERS // TODO “We should [add random

    task] in the future” // HACK “This works but is kinda hacky” // HERE BE DRAGONS
  4. COMMENTS USE YOUR OWN ANNOTATIONS @TechDebt(jira = "https://biowink.atlassian.net/browse/ATD-28") class BackupActivity

    : BaseActivity() { … } /** * The [TechDebt] annotation can be used… */ annotation class TechDebt(val jira: String)
  5. COMMENTS DO NOT COMMENT ▸ Constructors, getters, setters… Seriously! ▸

    Bad functions names. Fix them! ▸ Everything that can be inferred from the context and the code.
  6. COMMENTS FROM YOUR HEART TO YOUR CODE What you actually

    mean and should write: “Careful! This routine is not thread-safe!” What you might write while panicking or thinking you are funny or helpful: “Sh*t! This thing will blow up the moment 
 we start using threads! Fingers crossed!”
  7. COMMENTS FROM YOUR HEAD TO YOUR CODE scrollsSubscription = calendar

    .scrollEvents() .map { it.scrollState() } .filter { it == OnScrollListener.SCROLL_STATE_IDLE } .skip(5) .subscribe( { scrollsCount++ }, { Timber.e(it, "Scroll events observable died ") } )
  8. COMMENTS FROM YOUR HEAD TO YOUR CODE /* To be

    able to effectively track scroll events we start observing every scroll event we focus on the scroll state we ignore everything that's not [OnScrollListener.SCROLL_STATE_IDLE] we skip the first 5 events because Android fires 5 bogus events on screen loading we increment the counter that we will later use when the user navigates away from the screen. */ scrollsSubscription = calendar .scrollEvents() .map { it.scrollState() } .filter { it == OnScrollListener.SCROLL_STATE_IDLE } .skip(5) .subscribe( { scrollsCount++ }, { Timber.e(it, "Scroll events observable died ") } )
  9. COMMENTS FROM YOUR HEAD TO YOUR CODE interface AdsManager {

    fun hasPrefetchedAd(placement: Placement): Boolean }
  10. COMMENTS FROM YOUR HEAD TO YOUR CODE interface AdsManager {

    /** * This method checks if there is a prefetched ad for the given [placement]. * * @param placement the placement for which to check if a prefetched ad is * available * @return true if a prefetched ad for the given placement is available, * false otherwise */ fun hasPrefetchedAd(placement: Placement): Boolean }
  11. VARIABLES PACK INFORMATION IN THE NAME ▸Is being temporary the

    only actual quality of tmp? ▸If retval is a list of employees that we are returning, why don’t we call it employees? ▸Can those loop indexes improve the general readability somehow?
  12. VARIABLES HELPERS VARIABLES val email = … val username =

    email.toUsername() if (username == “root”) { … }
  13. FUNCTIONS SIDE NOTES ‣ Aim for small reusable functions ‣

    Aim for pure functions 1. Dependencies IN 2. Result OUT 3. No side effects
  14. IF THEN WHAT? THE ORDER ‣ Left: the expression being

    interrogated, the one more likely to change ‣ Right: the expression being compared against, the one that stays the same over time
  15. IF THEN WHAT? THE ORDER ‣ Positive case first ‣

    Simpler case first ‣ More interesting case first ‣ The case that returns earlier first
  16. IF THEN WHAT? TERNARY OPERATOR Given that lines are free

    When one single line can be replaced with four lines of more easy-to-understand code Then don't be a j*rk! ⚠
  17. IF THEN WHAT? TERNARY OPERATOR fun isUserOfAge(user: User?) = if

    (user == null) false else user.age >= 18
  18. THE USER PROFILE OBTAINING THE USER PROFILE fun loadUser(): Single<User>

    loadUser() .subscribeOn(Schedulers.io()) […]
  19. WRAPPING UP HEALTHY DEV TEAM TIPS ‣ YAGNI and KISS

    ‣ Keep your codebase small ‣ Create a routine of removing bad code ‣ Keep writing and maintaining your tests
  20. WRAPPING UP FURTHER READINGS ‣ The Art of Readable Code

    ‣ Working effectively with legacy code ‣ The pragmatic programmer ‣ Mini Habits: Smaller Habits, Bigger Results