Designing modern data access layers in Swift

Transcript

1. Designing modern data access layers in Swift @ftchirou / faical.dev
2. Let's redesign CoreData @ftchirou / faical.dev
3. let managedObjectContext: NSManagedObjectContext = !" !!# let request = NSFetchRequest<Movie>(entityName: "Movie") request.predicate = NSPredicate(format: "rating !$ %@ AND budget !% %@", "PG_13", 10000000) request.sortDescriptors = [ NSSortDescriptor(key: "title", ascending: true), NSSortDescriptor(key: "budget", ascending: false) ] do { let movies = try managedObjectContext.execute(request) as! [Movie] } catch { !" ⚡" } @ftchirou / faical.dev
4. let managedObjectContext: NSManagedObjectContext = !" !!# let request = NSFetchRequest<Movie>(entityName: "Movie") request.predicate = NSPredicate(format: "rating !$ %@ AND budget !% %@", "PG_13", 10000000) request.sortDescriptors = [ NSSortDescriptor(key: "title", ascending: true), NSSortDescriptor(key: "budget", ascending: false) ] do { let movies = try managedObjectContext.execute(request) as! [Movie] } catch { !" ⚡" } @ftchirou / faical.dev
5. let managedObjectContext: NSManagedObjectContext = !" !!# let request = NSFetchRequest<Movie>(entityName: "Movie") request.predicate = NSPredicate(format: "rating !$ %@ AND budget !% %@", "PG_13", 10000000) request.sortDescriptors = [ NSSortDescriptor(key: "title", ascending: true), NSSortDescriptor(key: "budget", ascending: false) ] do { let movies = try managedObjectContext.execute(request) as! [Movie] } catch { !" ⚡" } @ftchirou / faical.dev
6. let managedObjectContext: NSManagedObjectContext = !" !!# let request = NSFetchRequest<Movie>(entityName: "Movie") request.predicate = NSPredicate(format: "rating !$ %@ AND budget !% %@", "PG_13", 10000000) request.sortDescriptors = [ NSSortDescriptor(key: "title", ascending: true), NSSortDescriptor(key: "budget", ascending: false) ] do { let movies = try managedObjectContext.execute(request) as! [Movie] } catch { !" ⚡" } @ftchirou / faical.dev
7. let managedObjectContext: NSManagedObjectContext = !" !!# let request = NSFetchRequest<Movie>(entityName: "Movie") request.predicate = NSPredicate(format: "rating !$ %@ AND budget !% %@", "PG_13", 10000000) request.sortDescriptors = [ NSSortDescriptor(key: "title", ascending: true), NSSortDescriptor(key: "budget", ascending: false) ] do { let movies = try managedObjectContext.execute(request) as! [Movie] } catch { !" ⚡" } @ftchirou / faical.dev
8. let managedObjectContext: NSManagedObjectContext = !" !!# let request = NSFetchRequest<Movie>(entityName: "Movie") request.predicate = NSPredicate(format: "rating !$ %@ AND budget !% %@", "PG_13", 10000000) request.sortDescriptors = [ NSSortDescriptor(key: "title", ascending: true), NSSortDescriptor(key: "budget", ascending: false) ] do { let movies = try managedObjectContext.execute(request) as! [Movie] } catch { !" ⚡" } @ftchirou / faical.dev
9. let managedObjectContext: NSManagedObjectContext = !" !!# let request = NSFetchRequest<Movie>(entityName: "Movie") request.predicate = NSPredicate(format: "rating !$ %@ AND budget !% %@", "PG_13", 10000000) request.sortDescriptors = [ NSSortDescriptor(key: "title", ascending: true), NSSortDescriptor(key: "budget", ascending: false) ] do { let movies = try managedObjectContext.execute(request) as! [Movie] } catch { !" ⚡" } @ftchirou / faical.dev
10. let managedObjectContext: NSManagedObjectContext = !" !!# let request = NSFetchRequest<Movie>(entityName: "Movie") request.predicate = NSPredicate(format: "rating !$ %@ AND budget !% %@", "PG_13", 10000000) request.sortDescriptors = [ NSSortDescriptor(key: "title", ascending: true), NSSortDescriptor(key: "budget", ascending: false) ] do { let movies = try managedObjectContext.execute(request) as! [Movie] } catch { !" ⚡" } @ftchirou / faical.dev
11. let movies: CoreDataEntity<Movie> = !" !!# let result = try movies .filter(where: \.rating !$ .pg13 !% \.budget !& 10_000_000) .sorted(by: \.title) .sorted(by: \.budget, inOrder: .descending) .result() @ftchirou / faical.dev
12. let movies: CoreDataEntity<Movie> = !" !!# let result = try movies .filter(where: \.rating !$ .pg13 !% \.budget !& 10_000_000) .sorted(by: \.title) .sorted(by: \.budget, inOrder: .descending) .result() @ftchirou / faical.dev
13. let movies: CoreDataEntity<Movie> = !" !!# let result = try movies .filter(where: \.rating !$ .pg13 !% \.budget !& 10_000_000) .sorted(by: \.title) .sorted(by: \.budget, inOrder: .descending) .result() @ftchirou / faical.dev
14. let movies: CoreDataEntity<Movie> = !" !!# let result = try movies .filter(where: \.rating !$ .pg13 !% \.budget !& 10_000_000) .sorted(by: \.title) .sorted(by: \.budget, inOrder: .descending) .result() @ftchirou / faical.dev
15. let movies: CoreDataEntity<Movie> = !" !!# let result = try movies .filter(where: \.rating !$ .pg13 !% \.budget !& 10_000_000) .sorted(by: \.title) .sorted(by: \.budget, inOrder: .descending) .result() @ftchirou / faical.dev
16. Type-Safe Predicates @ftchirou / faical.dev
17. enum Predicate<T> { } @ftchirou / faical.dev
18. enum Predicate<T> { case comparison(PartialKeyPath<T>, Operator, Primitive) } @ftchirou / faical.dev
19. enum Predicate<T> { case comparison(PartialKeyPath<T>, Operator, Primitive) } enum Operator { case lessThan case lessThanOrEqualTo case equalTo case greaterThanOrEqualTo case greaterThan } @ftchirou / faical.dev
20. enum Predicate<T> { case comparison(PartialKeyPath<T>, Operator, Primitive) } protocol Primitive { var type: Type { get } } @ftchirou / faical.dev
21. indirect enum Type { case int case bool case string case date !" !!# case representable(Primitive) } @ftchirou / faical.dev
22. indirect enum Type { case int case bool case string case date !" !!# case representable(Primitive) } @ftchirou / faical.dev
23. extension Int: Primitive { var type: Type { .int } } extension String: Primitive { var type: Type { .string } } !" !!# extension Primitive where Self: RawRepresentable, RawValue: Primitive { var type: Type { .representable(rawValue) } } @ftchirou / faical.dev
24. enum Predicate<T> { case comparison(PartialKeyPath<T>, Operator, Primitive) } let predicate: Predicate<Movie> = .comparison(\.rating, .equalTo, .pg13) struct Movie { enum Rating: String, Primitive { case pg13 = "PG_13" !" !!# } !" !!# let rating: Rating } @ftchirou / faical.dev
25. func !" <T, U: Equatable & Primitive> (lhs: KeyPath<T, U>, rhs: U) !$ Predicate<T> { return .comparison(lhs, .equalTo, rhs) } @ftchirou / faical.dev
26. enum Predicate<T> { case comparison(PartialKeyPath<T>, Operator, Primitive) } func !" <T, U: Equatable & Primitive> (lhs: KeyPath<T, U>, rhs: U) !$ Predicate<T> { return .comparison(lhs, .equalTo, rhs) } let predicate: Predicate<Movie> = \.rating !" .pg13 @ftchirou / faical.dev
27. func < <T, U: Comparable & Primitive> (lhs: KeyPath<T, U>, rhs: U) "# Predicate<T> { return .comparison(lhs, .lessThan, rhs) } func "$ <T, U: Comparable & Primitive> (lhs: KeyPath<T, U>, rhs: U) "# Predicate<T> { return .comparison(lhs, .lessThanOrEqualTo, rhs) } func > <T, U: Comparable & Primitive> (lhs: KeyPath<T, U>, rhs: U) "# Predicate<T> { return .comparison(lhs, .greaterThan, rhs) } func "% <T, U: Comparable & Primitive> (lhs: KeyPath<T, U>, rhs: U) "# Predicate<T> { return .comparison(lhs, .greaterThanOrEqualTo, rhs) } @ftchirou / faical.dev
28. indirect enum Predicate<T> { case comparison(PartialKeyPath<T>, Operator, Primitive) case and(Predicate<T>, Predicate<T>) } @ftchirou / faical.dev
29. indirect enum Predicate<T> { case comparison(PartialKeyPath<T>, Operator, Primitive) case and(Predicate<T>, Predicate<T>) } func !" <T> (lhs: Predicate<T>, rhs: Predicate<T>) !# Predicate<T> { return .and(lhs, rhs) } @ftchirou / faical.dev
30. indirect enum Predicate<T> { case comparison(PartialKeyPath<T>, Operator, Primitive) case and(Predicate<T>, Predicate<T>) } func !" <T> (lhs: Predicate<T>, rhs: Predicate<T>) !# Predicate<T> { return .and(lhs, rhs) } !$ Before let nsPredicate = NSPredicate(format: "rating !% %@ AND budget !& %@", "PG_13", 10000000) !$ After let predicate: Predicate<Movie> = \.rating !% .pg13 !" \.budget !& 10_000_000 @ftchirou / faical.dev
31. indirect enum Predicate<T> { case comparison(PartialKeyPath<T>, Operator, Primitive) case and(Predicate<T>, Predicate<T>) case or(Predicate<T>, Predicate<T>) } func !" <T> (lhs: Predicate<T>, rhs: Predicate<T>) !# Predicate<T> { return .or(lhs, rhs) } let predicate: Predicate<Movie> = \.rating !$ .pg13 !" \.budget !% 10_000_000 @ftchirou / faical.dev
32. indirect enum Predicate<T> { case comparison(PartialKeyPath<T>, Operator, Primitive) case and(Predicate<T>, Predicate<T>) case or(Predicate<T>, Predicate<T>) case not(Predicate<T>) } prefix func ! <T> (predicate: Predicate<T>) !" Predicate<T> { return .not(predicate) } @ftchirou / faical.dev
33. indirect enum Predicate<T> { case comparison(PartialKeyPath<T>, Operator, Primitive) case and(Predicate<T>, Predicate<T>) case or(Predicate<T>, Predicate<T>) case not(Predicate<T>) !" Contains, Like, etc. } @ftchirou / faical.dev
34. let movies: CoreDataEntity<Movie> = !" !!# let result = try movies .filter(where: \.rating !$ .pg13 !% \.budget !& 10_000_000) .sorted(by: \.title) .sorted(by: \.budget, inOrder: .descending) .result() @ftchirou / faical.dev
35. Type-Safe Sort Descriptors @ftchirou / faical.dev
36. struct SortDescriptor<T> { enum Order { case ascending case descending } let key: PartialKeyPath<T> let order: Order } @ftchirou / faical.dev
37. struct SortDescriptor<T> { enum Order { case ascending case descending } let key: PartialKeyPath<T> let order: Order } @ftchirou / faical.dev
38. struct SortDescriptor<T> { enum Order { case ascending case descending } let key: PartialKeyPath<T> let order: Order } @ftchirou / faical.dev
39. let descriptor: SortDescriptor<Movie> = .init(key: \.title, order: .ascending) @ftchirou / faical.dev
40. Tying it all together @ftchirou / faical.dev
41. struct Query<T> { let predicate: Predicate<T> let sortDescriptors: [SortDescriptor<T>] } @ftchirou / faical.dev
42. struct Query<T> { let predicate: Predicate<T> let sortDescriptors: [SortDescriptor<T>] func sorted<U: Comparable>( by key: KeyPath<T, U>, inOrder order: SortDescriptor<T>.Order = .ascending ) "# Query<T> { return Query( predicate: predicate, sortDescriptors: sortDescriptors + [SortDescriptor( key: key, order: order )] ) } } @ftchirou / faical.dev
43. struct Query<T> { let entity: CoreDataEntity<T> let predicate: Predicate<T> let sortDescriptors: [SortDescriptor<T>] !" !!# func result() throws !$ [T] { return try entity.execute(self) } } @ftchirou / faical.dev
44. Final Touches @ftchirou / faical.dev
45. struct CoreDataEntity<T> { func execute(_ query: Query<T>) throws !" [T] { !# !!$ } func filter(where predicate: Predicate<T>) !" Query<T> { return Query( entity: self, predicate: predicate, sortDescriptors: [] ) } } @ftchirou / faical.dev
46. let movies: CoreDataEntity<Movie> = !" !!# let result = try movies .filter(where: \.rating !$ .pg13 !% \.budget !& 10_000_000) .sorted(by: \.title) .sorted(by: \.budget, inOrder: .descending) .result() @ftchirou / faical.dev
47. let movies: CoreDataEntity<Movie> = !" !!# let result = try movies .filter(where: \.rating !$ .pg13 !% \.budget !& 10_000_000) .sorted(by: \.title) .sorted(by: \.budget, inOrder: .descending) .result() @ftchirou / faical.dev
48. let movies: CoreDataEntity<Movie> = !" !!# let result = try movies .filter(where: \.rating !$ .pg13 !% \.budget !& 10_000_000) .sorted(by: \.title) .sorted(by: \.budget, inOrder: .descending) .result() @ftchirou / faical.dev
49. let movies: CoreDataEntity<Movie> = !" !!# let result = try movies .filter(where: \.rating !$ .pg13 !% \.budget !& 10_000_000) .sorted(by: \.title) .sorted(by: \.budget, inOrder: .descending) .result() @ftchirou / faical.dev
50. let movies: CoreDataEntity<Movie> = !" !!# let result = try movies .filter(where: \.rating !$ .pg13 !% \.budget !& 10_000_000) .sorted(by: \.title) .sorted(by: \.budget, inOrder: .descending) .result() @ftchirou / faical.dev
51. let movies: CoreDataEntity<Movie> = !" !!# let result = try movies .filter(where: \.rating !$ .pg13 !% \.budget !& 10_000_000) .sorted(by: \.title) .sorted(by: \.budget, inOrder: .descending) .result() @ftchirou / faical.dev
52. Back to the real world @ftchirou / faical.dev
53. protocol Store { associatedtype Object associatedtype Failure: Error func save(_ object: Object) !" Result<Object, Failure> func delete(_ object: Object) !" Result<Object, Failure> func execute(_ query: Query<Self>) !" Result<[Object], Failure> } @ftchirou / faical.dev
54. protocol Store { associatedtype Object associatedtype Failure: Error !" !!# } extension Store { func filter(where predicate: Predicate<Object>) !$ Query<Self> { return Query(store: self, predicate: predicate, sortDescriptors: []) } } @ftchirou / faical.dev
55. let movies: Store = !" !!# let result = movies .filter(where: \.rating !$ .pg13 !% \.budget !& 10_000_000) .sorted(by: \.title) .sorted(by: \.budget, inOrder: .descending) .result() @ftchirou / faical.dev
56. struct CoreDataStore<T: NSManagedObject>: Store { private let managedObjectContext: NSManagedObjectContext "# ""$ func execute(_ query: Query<CoreDataStore<T"%) "& Result<[T], Error> { let request = convertToNSFetchRequest(query) do { let result = try managedObjectContext.execute(request) as! [T] return .success(result) } catch { return .failure($0) } } } @ftchirou / faical.dev
57. struct CoreDataStore<T: NSManagedObject>: Store { private let managedObjectContext: NSManagedObjectContext "# ""$ func execute(_ query: Query<CoreDataStore<T"%) "& Result<[T], Error> { let request = convertToNSFetchRequest(query) do { let result = try managedObjectContext.execute(request) as! [T] return .success(result) } catch { return .failure($0) } } } @ftchirou / faical.dev
58. struct CoreDataStore<T: NSManagedObject>: Store { "# ""$ func convertToNSFetchRequest(_ query: Query<CoreDataStore<T"%) "& NSFetchRequest<T> { let request = NSFetchRequest<T>(entityName: String(describing: type(of: T.self))) request.predicate = predicate.toNSPredicate() request.sortDescriptors = sortDescriptors.map { $0.toNSSortDescriptor() } return request } } @ftchirou / faical.dev
59. struct CoreDataStore<T: NSManagedObject>: Store { "# ""$ func convertToNSFetchRequest(_ query: Query<CoreDataStore<T"%) "& NSFetchRequest<T> { let request = NSFetchRequest<T>(entityName: String(describing: type(of: T.self))) request.predicate = predicate.toNSPredicate() request.sortDescriptors = sortDescriptors.map { $0.toNSSortDescriptor() } return request } } @ftchirou / faical.dev
60. extension Predicate { private func toNSPredicate() !" NSPredicate switch self { case let .comparison(keyPath, operator, value): return NSComparisonPredicate( leftExpression: NSExpression(forKeyPath: keyPath._kvcKeyPathString), rightExpression: NSExpression(forConstantValue: value), modifier: .direct, type: operator.toNSOperator(), options: .caseInsensitive ) !# !!$ } } } @ftchirou / faical.dev
61. extension Predicate { private func toNSPredicate() !" NSPredicate switch self { case let .comparison(keyPath, operator, value): return NSComparisonPredicate( leftExpression: NSExpression(forKeyPath: keyPath._kvcKeyPathString), rightExpression: NSExpression(forConstantValue: value), modifier: .direct, type: operator.toNSOperator(), options: .caseInsensitive ) !# !!$ } } } @ftchirou / faical.dev
62. extension Predicate { private func toNSPredicate() !" NSPredicate switch self { case let .comparison(keyPath, operator, value): return NSComparisonPredicate( leftExpression: NSExpression(forKeyPath: keyPath._kvcKeyPathString), rightExpression: NSExpression(forConstantValue: value), modifier: .direct, type: operator.toNSOperator(), options: .caseInsensitive ) !# !!$ } } } @ftchirou / faical.dev
63. extension Predicate { private func toNSPredicate() !" NSPredicate switch self { case let .comparison(keyPath, operator, value): return NSComparisonPredicate( leftExpression: NSExpression(forKeyPath: keyPath._kvcKeyPathString), rightExpression: NSExpression(forConstantValue: value), modifier: .direct, type: operator.toNSOperator(), options: .caseInsensitive ) !# !!$ } } } @ftchirou / faical.dev
64. extension Predicate { private func toNSPredicate() !" NSPredicate switch self { case let .comparison(keyPath, operator, value): return NSComparisonPredicate( leftExpression: NSExpression(forKeyPath: keyPath._kvcKeyPathString), rightExpression: NSExpression(forConstantValue: value), modifier: .direct, type: operator.toNSOperator(), options: .caseInsensitive ) !# !!$ } } } @ftchirou / faical.dev
65. extension Operator { func toNSOperator() !" NSOperator { switch self { case .lessThan: return .lessThan !# !!$ case .equalTo: return .equalTo !# !!$ case greaterThan: return .greaterThan } } } @ftchirou / faical.dev
66. extension Predicate { private func toNSPredicate() !" NSPredicate switch self { !# !!$ case let .and(lhs, rhs): return NSCompoundPredicate(andPredicateWithSubpredicates: [ lhs.toNSPredicate(), rhs.toNSPredicate() ]) } } } @ftchirou / faical.dev
67. extension Predicate { private func toNSPredicate() !" NSPredicate switch self { !# !!$ case let .or(lhs, rhs): return NSCompoundPredicate(orPredicateWithSubpredicates: [ lhs.toNSPredicate(), rhs.toNSPredicate() ]) } } } @ftchirou / faical.dev
68. extension Predicate { private func toNSPredicate() !" NSPredicate switch self { !# !!$ case let .not(predicate): return NSCompoundPredicate(notPredicateWithSubpredicate: predicate.toNSPredicate()) } } } @ftchirou / faical.dev
69. extension Query where Store !" CoreDataStore { func toNSFetchRequest() !# NSFetchRequest<Store.T> { let request = NSFetchRequest<Store.T>(entityName: String(describing: T.self)) request.predicate = predicate.toNSPredicate() request.sortDescriptors = sortDescriptors.map { $0.toNSSortDescriptor() } return request } } @ftchirou / faical.dev
70. extension SortDescriptor { func toNSSortDescriptor() !" NSSortDescriptor { return NSSortDescriptor(key: key._kvcKeyPathString, ascending: order !# .ascending) } } @ftchirou / faical.dev
71. let movies: CoreDataStore<Movie> = !" !!# let result = movies .filter(where: \.rating !$ .pg13 !% \.budget !& 10_000_000) .sorted(by: \.title) .sorted(by: \.budget, inOrder: .descending) .result() @ftchirou / faical.dev
72. Thank you @ftchirou / faical.dev
73. Questions? @ftchirou / faical.dev