Swift Widget: getTimeline with completion handler - ios

Question

I have a iOS Widget that I am trying to update every 5 or 15 minutes.
I am new to widgets and do not understand how to loop the timeline with an async call.
struct SimpleEntry: TimelineEntry {
let date: Date
let configuration: ConfigurationIntent
let price: Double
}
func getTimeline(for configuration: ConfigurationIntent, in context: Context, completion: #escaping (Timeline<Entry>) -> ()) {
networkManager.fetchData { price in
var entries: [SimpleEntry] = []
let currentDate = Date()
for hourOffset in 0 ..< 5 {
let entryDate = Calendar.current.date(byAdding: .hour, value: hourOffset, to: currentDate)!
let entry = SimpleEntry(date: entryDate, configuration: configuration, price: price)
entries.append(entry)
}
let timeline = Timeline(entries: entries, policy: .atEnd)
completion(timeline)
}
}
I have a completion handler that passes in the price from the async api call.
networkManager.fetchData { price in
}

Answer 1

It looks like your networkManager.fetchData is providing only one price value at a time.
In such cases, when only one entry is provided at a time then the following should be enough:
func getTimeline(for configuration: ConfigurationIntent,
in context: Context,
completion: #escaping (Timeline<Entry>) -> ()) {
networkManager.fetchData { (price) in
let currentDate = Date()
//create the entry for the given price
let entry = SimpleEntry(date: currentDate,
configuration: configuration,
price: price)
/*
If you can predict price values then you need the loop for multiple entries.
However in your case, it seems this one entry is sufficient
*/
let entries = [entry]
//next reload date; 15mins in this case
let reloadDate = Calendar.current.date(byAdding: .minute,
value: 15,
to: currentDate)!
//your timeline with one entry that will refresh after given date
let timeline = Timeline(entries: entries, policy: .after(reloadDate))
completion(timeline)
}
}
By specifying after(_ date:) as the TimelineReloadPolicy, iOS will refresh the widget after the given date.
The timeline’s refresh policy specifies the earliest date for WidgetKit to request a new timeline from the provider. The default refresh policy, .atEnd, tells WidgetKit to request a new timeline after the last date in the array of timeline entries you provide. However, you can use .afterDate to indicate a different date either earlier or later than the default date. Specify an earlier date if you know there’s a point in time before the end of your timeline entries that may alter the timeline.
Ref: Apple Documentation on Timeline
This solution was to address the core issue, so finally I would like to add a disclaimer that reloading every 15mins might be overkill. Hence tweak your logic to specify the TimelineReloadPolicy intelligently. If you can predict values & create a timeline of multiple entries with fewer network calls then great! If not then... well... best of luck :)
Important
Plan ahead if your widget makes requests to a server when it reloads, and uses afterDate() with a specific date in timeline entries. WidgetKit tries to respect the date you specify, which may cause a significant increase in server load when multiple devices reload your widget at around the same time.
Ref: Keeping a Widget Up To Date
More Read:
Apple Documentation on TimelineProvider