watchOS: Complications

Feb 7 2023 · Swift 5.6, watchOS 8.5, Xcode 13

Part 1: Introduction to Complications

03. Update a Complication's Data

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Previous episode: 02. Create Your First Complication Next episode: 04. Support Multiple Families

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Add sample data

So. The current timeline entry isn’t showing up in this list.

func localizableSampleTemplate(
  for complication: CLKComplication
) async -> CLKComplicationTemplate? {

  guard == .graphicCircular,
    let image = UIImage(named: "tide_rising")
  else {
    return nil
  let tide = Tide(entity: Tide.entity(), insertInto: nil) = Date()
  tide.height = 24
  tide.type = .high
  return CLKComplicationTemplateGraphicCircularStackImage(
    line1ImageProvider: .init(fullColorImage: image),
    line2TextProvider: .init(format: tide.heightString())

Updating the complication’s data

When people first learn about complications, the missing “Ah-ha!” moment is that the Apple Watch will only attempt to update the complication on the watch face when you specify that new data is available.

Telling watchOS there’s new data

Open CoOpsApi.swift, and you’ll see getLowWaterHeights(), the method the app calls when it needs to download new tide data.

import ClockKit
DispatchQueue.main.async {
  let server = CLKComplicationServer.sharedInstance()

Providing data to the complication

Ok! Switch back to ComplicationController.swift

guard == .graphicCircular🟩,
  let tide = Tide.getCurrent()🔴
else {...
let template = 🟩CLKComplicationTemplateGraphicCircularStackImage(
  line1ImageProvider: .init(fullColorImage: tide.image()),
  line2TextProvider: .init(format: tide.heightString())
return .init(date: 🟩, complicationTemplate: template)