Enable strict concurrency checking

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.8
+// swift-tools-version:6.0
 
 //
 // This source file is part of the OMHModels open source project
@@ -8,18 +8,19 @@
 // SPDX-License-Identifier: MIT
 //
 
+import class Foundation.ProcessInfo
 import PackageDescription
 
 
 let package = Package(
     name: "OMHModels",
     platforms: [
         .iOS(.v16),
-        .watchOS(.v9)
     ],
     products: [
         .library(name: "OMHModels", targets: ["OMHModels"])
     ],
+    dependencies: swiftLintPackage(),
     targets: [
         .target(
             name: "OMHModels"
@@ -28,7 +29,26 @@ let package = Package(
             name: "OMHModelsTests",
             dependencies: [
                 .target(name: "OMHModels")
-            ]
+            ],
+            plugins: [] + swiftLintPlugin()
         )
     ]
 )
+
+
+func swiftLintPlugin() -> [Target.PluginUsage] {
+    // Fully quit Xcode and open again with `open --env SPEZI_DEVELOPMENT_SWIFTLINT /Applications/Xcode.app`
+    if ProcessInfo.processInfo.environment["SPEZI_DEVELOPMENT_SWIFTLINT"] != nil {
+        [.plugin(name: "SwiftLintBuildToolPlugin", package: "SwiftLint")]
+    } else {
+        []
+    }
+}
+
+func swiftLintPackage() -> [PackageDescription.Package.Dependency] {
+    if ProcessInfo.processInfo.environment["SPEZI_DEVELOPMENT_SWIFTLINT"] != nil {
+        [.package(url: "https://github.com/realm/SwiftLint.git", from: "0.55.1")]
+    } else {
+        []
+    }
+}

Sources/OMHModels/DateTime.swift

@@ -12,17 +12,13 @@ import Foundation
 public struct DateTime: Schema, Equatable {
     /// The Open mHealth schema identifier
     public static let schemaId = SchemaId(namespace: .ieee, name: "date-time", version: "1.0")
-
-    private static let formatter: ISO8601DateFormatter = {
-        let formatter = ISO8601DateFormatter()
-        return formatter
-    }()
 
     let value: String // The value should be in ISO8601 format as per the schema.
 
 
     public init(date: Date) {
-        self.value = DateTime.formatter.string(from: date)
+        let formatter = ISO8601DateFormatter()
+        self.value = formatter.string(from: date)
     }
 
     public init(from decoder: Decoder) throws {