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API Design as an Art Zac Sweers - Uber @pandanomic

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aWhat makes ana API?

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aWhat makes ana API bad?

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Developer experience API Design

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Developer experience API Design

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aWhat makes ana API bad?

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What makes an API good? !

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What makes an API good?

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⛏

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Your lib Picasso Dagger ROOM Support library Internal libs Butter Knife RxJava Kotlin ⛏

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AutoDispose

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AutoDispose • RxJava 2 utility for automatic stream disposal

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AutoDispose • RxJava 2 utility for automatic stream disposal • Originally built in a side project ~10/2016

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AutoDispose • RxJava 2 utility for automatic stream disposal • Originally built in a side project ~10/2016 • Mainlined to Uber ~12/2016

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AutoDispose • RxJava 2 utility for automatic stream disposal • Originally built in a side project ~10/2016 • Mainlined to Uber ~12/2016 • Open sourced 3/2017

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Observable.just(1) .subscribe()

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apiRequest() .subscribe()

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apiRequest() // 200+ ms .subscribe()

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apiRequest() // 200+ ms .subscribeOn(io()) .observeOn(mainThread()) .subscribe()

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apiRequest() // 200+ ms .subscribeOn(io()) .observeOn(mainThread()) .subscribe() // DetailActivity.kt Memory leak

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val disposable = apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe()

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val disposable = apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe() // Later disposable.dispose()

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val disposable = apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe()

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe()

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose.with(this).forObservable()) .subscribe()

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose .with(this) // Scope .forObservable()) // Type .subscribe()

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose .with(this) // Scope .forObservable()) // Type .subscribe()

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose .with(this) // Scope .forObservable()) // Type .subscribe()

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose .with(this) // Scope .forObservable()) // Type .subscribe()

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose .with(this) // Scope .forObservable()) // Type .subscribe()

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose .with(this) .forObservable()) .subscribe()

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose .with(Maybe.never()) .forObservable()) .subscribe()

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose .with(this) .forObservable()) .subscribe()

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose .with(this) // ScopeProvider .forObservable()) .subscribe()

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interface ScopeProvider { fun requestScope(): Maybe<*> }

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interface LifecycleScopeProvider { fun correspondingEvents(): Function fun peekLifecycle(): E fun lifecycle(): Observable }

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interface ScopeProvider { fun requestScope(): Maybe<*> }

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose .with(this) // ScopeProvider .forObservable()) .subscribe()

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe()

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe() .disposeOn(lifecycle)

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe { // Stuff } .disposeOn(lifecycle)

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe { // Stuff // Stuff // Stuff // Stuff // Stuff // Stuff }

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe { // Stuff // Stuff // Stuff // Stuff // Stuff // Stuff } .disposeOn(lifecycle)

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe({ r -> // Handle response }) { error: Throwable -> // Stuff // Stuff } .disposeOn(lifecycle)

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .delaySubscription(attaches()) .subscribe() .disposeOn(lifecycle)

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .delaySubscription(attaches()) .subscribe(myObserver) .disposeOn(lifecycle)

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .delaySubscription(attaches()) .subscribe(myObserver) .disposeOn(lifecycle)

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe()

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe(BoundObservers.forObservable(lifecycle) .onNext(...) .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .onNext(...) .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .onNext(...) .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .onNext(...) .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .onNext(...) .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .onNext(...) .onError(...) .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .onNext(...) .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .onNext(...) .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .onNext(...) .onError(...) .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .onNext(...) .onError(...) .onComplete(...) .create())

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.subscribe()

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.subscribe(BoundObservers.forObservable(lifecycle) .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .onNext(Object o -> ???) // ಠ_ಠ .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .onNext(Object o -> ???) // ಠ_ಠ .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .onNext(Response r -> ...) // :D .create())

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.subscribe(BoundObservers.forObservable(lifecycle) .create())

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ResponseObserver o = ResponseObserver() .subscribe(BoundObservers.forObservable(lifecycle) .create())

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class ResponseObserver : BoundObserver() { // :( }

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ResponseObserver o = ResponseObserver() .subscribe(BoundObservers.forObservable(lifecycle) .create())

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ResponseObserver o = ResponseObserver() PublishSubject sub = PublishSubject.create() .subscribe(BoundObservers.forObservable(lifecycle) .create())

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PublishSubject sub = PublishSubject.create() .subscribe(BoundObservers.forObservable(lifecycle) .create())

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PublishSubject sub = PublishSubject.create() .subscribe(BoundObservers.forObservable(lifecycle) .around(sub))

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PublishSubject sub = PublishSubject.create() .subscribe(BoundObservers.forObservable(lifecycle) .around(sub))

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PublishSubject sub = PublishSubject.create() .subscribe(BoundObservers.forObservable(lifecycle) .onNext(...) .around(sub))

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PublishSubject sub = PublishSubject.create() .subscribe(BoundObservers.forObservable(lifecycle) .onNext(...) .around(sub))

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PublishSubject sub = PublishSubject.create() .subscribe(BoundObservers.forObservable(lifecycle) .onNext(...) .onNext(...) .onNext(...) .onNext(...) .onNext(...) .onNext(...) .onNext(...) .around(sub))

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.subscribe(BoundObservers.forObservable(lifecycle) .create())

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.subscribe(AutoDispose.forObservable(lifecycle) .create())

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.subscribe(AutoDispose.forObservable(lifecycle) .around(...))

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fun around(o: Observer) fun around(c: Consumer) fun around(c: Consumer, e: Consumer) fun around(c: Consumer, e: Consumer, a: Action) // Etc

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fun around(o: Observer) fun around(c: Consumer) fun around(c: Consumer, e: Consumer) fun around(c: Consumer, e: Consumer, a: Action) fun empty() // Etc

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interface AroundClause { fun around(o: Observer) fun around(c: Consumer) fun around(c: Consumer, e: Consumer) fun around(c: Consumer, e: Consumer, a: Action) fun empty() // Etc }

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ResponseObserver o = new ResponseObserver() .subscribe(AutoDispose.forObservable(lifecycle) .around(o)) V2 : AroundClause

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ResponseObserver o = new ResponseObserver() .subscribe(AutoDispose.forObservable(lifecycle) .around(o))

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ResponseObserver o = new ResponseObserver() .subscribe(AutoDispose.observable() .scopeWith(lifecycle) .around(o)) V3

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ResponseObserver o = new ResponseObserver() .subscribe(AutoDispose.observable() .scopeWith(scope) .around(o)) V3

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ResponseObserver o = new ResponseObserver() .subscribe(AutoDispose.observable() .scopeWith(scope) .around(o))

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ResponseObserver o = new ResponseObserver() .subscribe(AutoDispose.observable() .scopeWith(scope) .around(o))

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ResponseObserver o = new ResponseObserver() .subscribe(AutoDispose.observable() .scopeWith(scope) .around(o))

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ResponseObserver o = new ResponseObserver() .subscribe(AutoDispose.observable() .scopeWith(scope) .around(o))

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interface AroundClause { fun around(o: Observer) fun around(c: Consumer) fun around(c: Consumer, e: Consumer) fun around(c: Consumer, e: Consumer, a: Action) fun empty() // Etc }

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interface AroundClause { fun around(o: Observer) fun around(c: Consumer) fun around(c: Consumer, e: Consumer) fun around(c: Consumer, e: Consumer, a: Action) fun empty() // Etc }

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ResponseObserver o = new ResponseObserver() .subscribe(AutoDispose.observable() .scopeWith(scope) .around(o))

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ResponseObserver o = new ResponseObserver() .subscribe(AutoDispose.observable() .scopeWith(scope) .around(o))

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ResponseObserver o = new ResponseObserver() .subscribe(AutoDispose.observable() .scopeWith(scope) .around(new Consumer() { // Impl }))

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe(AutoDispose.observable() .scopeWith(scope) .around(new Consumer() { // Impl })) V4

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe(AutoDispose.observable() .scopeWith(scope) .around(new Consumer() { // Impl }))

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe(AutoDispose.observable() .scopeWith(scope) .around(new Consumer() { @Override public void accept(Response r) { handleResponse(r) } }))

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.to()

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.to(new Function, ???>() {})

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.to(new Function, AroundClause>() {})

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .subscribe(AutoDispose.observable() .scopeWith(scope) .around(new Consumer() { @Override public void accept(Response r) { handleResponse(r) }x }))

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(???) .subscribe(AutoDispose.observable() .scopeWith(scope) .around(new Consumer() { @Override public void accept(Response r) { handleResponse(r) }x }))

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(???) .around(new Consumer() { @Override public void accept(Response r) { handleResponse(r) }x }))

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose.observable() .scopeWith(scope)) .around(new Consumer() { @Override public void accept(Response r) { handleResponse(r) }x }))

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose.observable() .scopeWith(scope)) .around(new Consumer() { @Override public void accept(Object r) { handleResponse(r) }x }))

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose.observable() .scopeWith(scope)) .around(new Consumer() { @Override public void accept(Object r) { // (╯°□°）╯︵ ┻━┻ }x }))

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class ObservableScoper implements Function, AroundClause> { }v

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class ObservableScoper implements Function, AroundClause> { ObservableScoper(Maybe> scope) { // ... }a }v

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class ObservableScoper implements Function, AroundClause> { ObservableScoper(Maybe> scope) { // ... }a @Override public AroundClause apply(Observable o) { }b }v

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class ObservableScoper implements Function, AroundClause> { ObservableScoper(Maybe> scope) { // ... }a @Override public AroundClause apply(Observable o) { return new AroundClause() { // ... }c }b }v

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class ObservableScoper implements Function, AroundClause> { ObservableScoper(Maybe> scope) { // ... }a @Override public AroundClause apply(Observable o) { return new AroundClause() { // ... }c }b }v

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(new ObservableScoper(scope)) .around(new Consumer() { @Override public void accept(Response r) { handleResponse(r) } }))

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interface AroundClause { fun around(o: Observer) fun around(c: Consumer) fun around(c: Consumer, e: Consumer) fun around(c: Consumer, e: Consumer, a: Action) fun empty() // Etc }

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interface SubscribeProxy { fun around(o: Observer) fun around(c: Consumer) fun around(c: Consumer, e: Consumer) fun around(c: Consumer, e: Consumer, a: Action) fun empty() // Etc }

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interface SubscribeProxy { fun subscribe(o: Observer) fun subscribe(c: Consumer) fun subscribe(c: Consumer, e: Consumer) fun subscribe(c: Consumer, e: Consumer, a: Action) fun empty() // Etc }

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interface SubscribeProxy { fun subscribe(o: Observer) fun subscribe(c: Consumer) fun subscribe(c: Consumer, e: Consumer) fun subscribe(c: Consumer, e: Consumer, a: Action) fun subscribe() // Etc }

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(new ObservableScoper(scope)) .around(new Consumer() { @Override public void accept(Response r) { handleResponse(r) } }))

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(new ObservableScoper(scope)) .subscribe(new Consumer() { @Override public void accept(Response r) { handleResponse(r) } }))

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–Nick Butcher, and probably other people “If it looks right, it is right.”

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(new ObservableScoper(scope)) .subscribe(newxConsumer() { @Override public void accept(Response r) { handleResponse(r) }x })) V5

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose.with(scope).forObservable()) .subscribe(newxConsumer() { @Override public void accept(Response r) { handleResponse(r) }x }))

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose.with(scope).forObservable()) .subscribe(new Consumer() { @Override public void accept(Response r) { handleResponse(r) }x }))

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose.forObservable(scope)) .subscribe(new Consumer() { @Override public void accept(Response r) { handleResponse(r) }x }))

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https://youtrack.jetbrains.com/issue/ IDEA-179864

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apiRequest() .subscribeOn(io()) .observeOn(mainThread()) .to(AutoDispose.forObservable(scope)) .subscribe(new Consumer() { @Override public void accept(Response r) { handleResponse(r) }x }))

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aWhat makes ana API good? !

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“Prefer exposing interfaces”

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“Prefer exposing interfaces” interface SubscribeProxy { fun subscribe(o: Observer) fun subscribe(c: Consumer) fun subscribe(c: Consumer, e: Consumer) fun subscribe(c: Consumer, e: Consumer, a: Action) fun subscribe() // Etc }

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“Prefer composition in accepting external implementations. Inheritance can be inconvenient.”

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“Prefer composition in accepting external implementations. Inheritance can be inconvenient.” class ResponseObserver : BoundObserver() { // :( } PublishSubject sub = PublishSubject.create()

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“Prefer final by default”

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“Identify footguns”

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“Identify footguns” .subscribe(BoundObservers.forObservable(lifecycle) .onNext(...) .onNext(...) .onNext(...) .onNext(...) .onNext(...) .onNext(...) .onNext(...) .around(sub))

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“Dependency on lint should be avoided”

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“Dependency on lint should be avoided”

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“IDE experience matters”

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“IDE experience matters” .around(new Consumer() { @Override public void accept(Object r) { // (╯°□°）╯︵ ┻━┻ }x }))

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“Crack eggs, make omelettes” V4 V5 V0 V3 V1

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Questions? Zac Sweers - Uber @pandanomic