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A playground for Xcode to test a custom date decoding strategy
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| import Foundation | |
| // MARK: Extension on Formatter to provide ISO8601DateFormatter instances | |
| extension Formatter { | |
| static let iso8601: ISO8601DateFormatter = { | |
| let formatter = ISO8601DateFormatter() | |
| // This options is the default (can be omitted but but I prefer to make it explicit) | |
| formatter.formatOptions = [.withFractionalSeconds] | |
| return formatter | |
| }() | |
| static let iso8601withFractionalSeconds: ISO8601DateFormatter = { | |
| let formatter = ISO8601DateFormatter() | |
| formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds] | |
| return formatter | |
| }() | |
| } | |
| // MARK: Custom date decoding strategy | |
| extension JSONDecoder.DateDecodingStrategy { | |
| static let customISO8601Cascade = custom { | |
| let container = try $0.singleValueContainer() | |
| let string = try container.decode(String.self) | |
| if let date = Formatter.iso8601withFractionalSeconds.date(from: string) ?? Formatter.iso8601.date(from: string) { | |
| return date | |
| } | |
| throw DecodingError.dataCorruptedError(in: container, debugDescription: "Invalid date: \(string)") | |
| } | |
| } | |
| // MARK: Data models | |
| struct Event: Decodable { | |
| let id: Int | |
| let timestamp: Date | |
| } | |
| struct EventsResponse: Decodable { | |
| let events: [Event] | |
| } | |
| // MARK: Usage example | |
| let jsonData = """ | |
| { | |
| "events": [ | |
| { "id": 1, "timestamp": "2025-09-05T13:25:41Z" }, | |
| { "id": 2, "timestamp": "2025-09-01T09:53:38.000Z" }, | |
| { "id": 3, "timestamp": "2025-09-18T21:54:22.923456Z" } | |
| ] | |
| } | |
| """.data(using: .utf8)! | |
| do { | |
| let decoder = JSONDecoder() | |
| decoder.dateDecodingStrategy = .customISO8601Cascade | |
| let response = try decoder.decode(EventsResponse.self, from: jsonData) | |
| response.events.forEach { print("\($0.id): \($0.timestamp)") } | |
| } catch { | |
| print("Decoding failed:", error) | |
| } |
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