The Challenges of Building a Database API (in Swift)

Presented at 360i|Dev 2015.

Transcript

1. The Challenges of Building a Database API (In Swift) Samuel Giddins
2. Samuel Giddins Cocoa Binding Engineer @ Realm CocoaPods, Bundler, Jazzy, RestKit, etc.
3. Turbocharger for other developers
4. Realm — Fast, zero-copy, embedded database built from the ground up for mobile — Used in apps with hundreds of millions of users — NoSQL (as in, no SQL) — Fully ACID transactions — Well-defined threading model — Cross-platform C++ core with many language bindings (currently Objective-C, Swift, & Android)
7. Swift — Strongly typed — Staticly inclined — Objective-C interop — Syntactically concise
8. Databases Defined by a few different questions: — What's the atomic unit? — How do you interact with your data? — What's implicit? What's explicit? — What do you optimize for? — Performance — Code — Safety — Concurrency
9. Databases So much is about the API. Implementing the storage engine is hard enough, but it's the easy part.
10. Databases — Are at the center of almost every mobile app. — They're used everywhere in an app. — Perhaps the cornerstone.
11. Existing Approaches — Core Data — sqlite.h — Redis — SQL — ActiveRecord — Sequel — Realm Objective-C
12. But what about !?
13. Swift Features — Optionals — Generics & Type Inference — Enums — Structs / Value Types — Static Compiler ✨
14. Realm Objective-C Features — Swizzling — Runtime introspection — Laziness — Autoreleasepool-based caching — Native "dynamic" API — On-demand class creation
16. aka Impedence Mismatch
17. Sacrifices — Type safety — String — AnyObject — Queries — Struct value semantics — Non-RawRepresentable enums — Error handling
18. The Objective-C API we've always wanted
19. class Book: Object { dynamic var name = "" // needs default for schema initialization dynamic var pageCount: Int = 0 dynamic var author: Author? override class func primaryKey() -> String { return "name" } } let realm = Realm() let books = realm.objects(Book).filter("pageCount > 50").sort("name") let book = Book(value: ["name" : "The Name of the Wind"]) book.author = books.filter("name = %@", "The Wise Man's Fear").first?.author book.pageCount = 994 realm.write { realm.add(book) realm.create(Book.self, book, update: true) }
20. There are lots of beginners.
21. Approachability — Not everyone is a Haskell wizard — Programmers get objects — Boilerplate => !
22. let realm = Realm() var writeTransaction = realm.beginWrite() let table = writeTransaction.table(Book) writeTransaction.set(table, 0, Book.Properties.Name, "Catch-22") realm.commitWrite(writeTransaction)
24. let book = Book() book.name = "Cien Años de Soledad" book.pageCount = 324 do { let realm = try Realm() realm.write { realm.add(book, update: true) } } catch { // handle error }
25. Dynamic — Normally means slow — Slower than static — Faster than string-based lookups — Flexible — Can bind to column indices at runtime — Allows for "standalone" objects
26. Dynamic — Limited to "Objective-C types" — No List<Book> — No Int? — No String? — Yes Author? — Requires var — Can be lying to the compiler — No way to enforce — Confusing when a property isn't persisted
27. book.name = book.name + ": Part Deux" => — Load book name — Translate to NSString — Append — Store new book name
28. Underlying operations still hidden
30. Reporting failures — NSErrorPointer — throws — fatalError — Optional<T> — throwRealmException
31. Testing — Handling failure modes — Code that shouldn't compile — Using generics — Looks nothing like user code
32. Months in the making — jp-swift-xcode-beta-7 — jp-swift — tg-swift — al-swift — al-al-swift — master
33. !
34. ! — CocoaPods — Carthage — Module Maps — Nested Frameworks — Xcodes & Swift Versions — Documentation
35. The Verdict
36. The Verdict — Nicest Realm API yet — Least cooperative language — Relying on interop is !/" — Prototype something else — Eventually
37. The Verdict What's Missing — Native metaprogramming — Dynamic structs — API / ABI / Tooling -- stability / compatibility — C++ interop — Property properties — Threading in the type system
38. The Verdict Swift isn't ready for this
39. Yet
40. Give us one or two more features, and a few years, and Swift could give us the perfect platform for building expressive, concise, powerful, & performant APIs.
41. Samuel Giddins Cocoa @ Realm @segiddins