Swift: task {} before iOS 15? - swift

Question

I am following tutorials to understand SwiftUI, and specifically how to call an API when a view appears.
I saw this:
List(results, id: \.trackId) { item in
ListRow(item)
}
.task {
// perform API here
}
But as my app targets iOS 14, I get this error:
'task(priority:_:)' is only available in iOS 15.0 or newer
So what could I do instead? Thank you for your help

Answer 1

You can write a version of task { } that works for iOS 13, iOS 14 and uses apple's version for iOS 15:
extension View {
#available(iOS, deprecated: 15.0, message: "This extension is no longer necessary. Use API built into SDK")
func task(priority: TaskPriority = .userInitiated, _ action: #escaping #Sendable () async -> Void) -> some View {
self.onAppear {
Task(priority: priority) {
await action()
}
}
}
}

Answer 2

async await is available for iOS 13+.
https://developer.apple.com/documentation/swift/task
if you need to use an async call is wrap the call in Task
.onAppear(){
Task{
//Your async code here
// await yourFuncHere()
}
}
.onAppear is a bit un reliable so I might opt for an init of an ObservableObject as an alternative.

Answer 3

Just switching to .onAppear is not correct since it's missing the point of Structured Concurrency. Every time you create a Task yourself you should be suspicious, you are doing something out of the ordinary.
Granted, in this case we don't have available a "structured concurrency aware" lifecycle modifier, so we need to make our own with Task init, but that means you need to be responsible of respecting structured concurrency!
This means that getting a proper backwards compatible solution to work is a bit more code, since you want to handle cancellation properly. For that you need to use also .onDisappear and cancel the task that you started on .onAppear.
If you want to have it reusable you can make a custom .task modifier.

Answer 4

import SwiftUI
struct ContentView: View {
#State var results = [TaskEntry]()
var body: some View {
List(results, id: \.id) { item in
VStack(alignment: .leading) {
Text(item.title)
}
// this one onAppear you can use it
}.onAppear(perform: loadData)
}
func loadData() {
guard let url = URL(string: "https://jsonplaceholder.typicode.com/todos") else {
print("Your API end point is Invalid")
return
}
let request = URLRequest(url: url)
URLSession.shared.dataTask(with: request) { data, response, error in
if let data = data {
if let response = try? JSONDecoder().decode([TaskEntry].self, from: data) {
DispatchQueue.main.async {
self.results = response
}
return
}
}
}.resume()
}
}