Add formatter for a11y string

ScienceJournal/Extensions/DateComponentsFormatter+ScienceJournal.swift

@@ -27,4 +27,23 @@ extension DateComponentsFormatter {
     return formatter
   }
 
+  /// Returns an accessible string based on the given time interval, appending any available
+  /// fractional seconds as milliseconds using a NSCalendar.Unit.spellOut unitsStyle.
+  ///
+  /// - Parameters:
+  ///   - ti: The time interval, measured in seconds. The value must be a finite number.
+  ///     Negative numbers are treated as positive numbers when creating the string.
+  ///   - fractional: The fractional seconds available on the time interval.
+  ///     If this equals 0, milliseconds will not be appended to the string.
+  /// - Returns: A formatted string representing the specified time interval.
+  func string(from ti: TimeInterval, appending fractional: Int64) -> String {
+    guard let duration = TimeInterval.accessibleIntervalFormatter.string(from: ti) else {
+        return ""
+    }
+    if fractional > 0 {
+        return duration + " \(fractional) " + String.timeIntervalMilliseconds
+    }
+    return duration
+  }
+
 }

ScienceJournal/Extensions/TimeInterval+ScienceJournal.swift

@@ -35,10 +35,19 @@ extension TimeInterval {
   }
 
   /// Returns the time interval as an accessible string in component format with hours, minutes and
-  /// seconds without abbreviation.
-  /// Example: "One hour 46 minutes 11 seconds"
+  /// seconds without abbreviation.  When there are fractional seconds present on the time interval,
+  /// this will include them as milliseconds.
+  /// Example: "One hour 46 minutes 11 seconds" and "One second 250 milliseconds".
   var accessibleDurationString: String {
-    return TimeInterval.accessibleIntervalFormatter.string(from: self) ?? ""
+    return TimeInterval.accessibleIntervalFormatter.string(from: self, appending: fractional)
+  }
+
+  /// The fractional seconds available on the time interval.
+  /// Example: 250 when the time interval equals 1.250, and 0 when the time interval equals 3.0.
+  private var fractional: Int64 {
+    let remainder = truncatingRemainder(dividingBy: 1)
+    guard remainder > 0.0 else { return 0 }
+    return Int64(remainder * 1000)
   }
 
 }

ScienceJournal/Resources/Strings.bundle/en.lproj/Localizable.strings

@@ -1381,6 +1381,9 @@
 /* Accessibility hint for a graphic representing an in-progress recording, telling a user that interacting with it will show the observe tab [CHAR_LIMIT=NONE] */
 "throbber_content_details" = "Double tap to switch to the observe tab in the tool drawer";
 
+/* Name for milliseconds in a TimeInterval object */
+"time_interval_milliseconds" = "milliseconds";
+
 /* Title for activity that handles sensor settings [CHAR_LIMIT=40] */
 "title_activity_sensor_settings" = "Sensor settings";
 

ScienceJournal/Strings/ScienceJournalStrings.swift

@@ -485,6 +485,7 @@ extension String {
   static public var textNoteAddedContentDescription: String { return "text_note_added_content_description".localized }
   static public var throbberContentDescription: String { return "throbber_content_description".localized }
   static public var throbberContentDetails: String { return "throbber_content_details".localized }
+  static public var timeIntervalMilliseconds: String { return "time_interval_milliseconds".localized }
   static public var titleActivitySensorSettings: String { return "title_activity_sensor_settings".localized }
   static public var toExperimentContentDescription: String { return "to_experiment_content_description".localized }
   static public var toRunContentDescription: String { return "to_run_content_description".localized }

ScienceJournalTests/Extensions/TimeInterval+ScienceJournalTest.swift

@@ -30,4 +30,9 @@ class TimeInterval_ScienceJournalTest: XCTestCase {
     XCTAssertEqual(interval.accessibleDurationString, "one hour, three minutes, twelve seconds")
   }
 
+  func testAccessibleDurationStringWithFractionalSeconds() {
+    let interval: TimeInterval = 1.250
+    XCTAssertEqual(interval.accessibleDurationString, "one second 250 milliseconds")
+  }
+
 }