I came across some old code I had in a project and I can't understand what is happening:
var str = "blah"
let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
print(response)
var err: NSError?
do {
let myJson = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.mutableContainers) //as [[String:Any]]
print(myJson)
str = String(describing: myJson)
Task {
await MainActor.run {() -> Void in
self.m_textView.string = str
}}
} catch let error as NSError {
err = error
}
}.resume()
So how to parse this? Because at the end of the block we see the resume() being called. Does the resume() return a Task object? No. I just remembered that a block at the end is actually passed as the last parameter to the function being called (dataTask()). So what returns a task object is the call to dataTask() not the call to resume(). This syntactic sugar can be confusing!
But on second thought resume() is only called on a Task() object right? So is the .resume() actually being called on the result of "let task ="? Ugh.
This is one of the reasons I hate swift. What code does is not obvious.
Ok, I found some sample code on Apple's site which is clearer:
func startLoad() {
let url = URL(string: "https://www.example.com/")!
let task = URLSession.shared.dataTask(with: url) { data, response, error in
if let error = error {
self.handleClientError(error)
return
}
guard let httpResponse = response as? HTTPURLResponse,
(200...299).contains(httpResponse.statusCode) else {
self.handleServerError(response)
return
}
if let mimeType = httpResponse.mimeType, mimeType == "text/html",
let data = data,
let string = String(data: data, encoding: .utf8) {
DispatchQueue.main.async {
self.webView.loadHTMLString(string, baseURL: url)
}
}
}
task.resume()
}
