In method A, get data from callback in method B? - swift

Question

I have a function that is build to get the latest items from a API. There are several other ones, with different functionality, but they all work the same. It looks like this:
func getLatest(pageNumber: Int) -> Array<Any>{
let urlRequest = URL(string: baseUrl + latestUrl + String(pageNumber))
let requestedData = doRequest(url: urlRequest!, completion: { data -> Void in
// We have the data from doRequest stored in data, but now what?!
})
return allData
}
I also have a async method that handles the requests. That one looks like this:
func doRequest(url: URL, completion: #escaping ([[ApiItem]]) -> ()){
var allItems = [[ApiItem]]()
URLSession.shared.dataTask(with: url) { (data, response, error) in
guard let data = data else { return }
do{
let json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as! [String: AnyObject]
let results = json["items"] as? [AnyObject]
for r in results!{
let item = ApiItem(json: r as! [String: Any])
allItems.append([item])
}
completion(allItems)
} catch let jsonError{
print("JSON error: \(jsonError)")
}
}.resume()
The doRequest function works absolutely fine. It gets the data, parses the JSON and send it back to getLatest --> requestedData. The problem right now is, is that getLatest() is a function that needs to return the data that is stored in the data variable of requestedData.
How can I make it so, that the getLatest() function returns the data that is stored in the data in requestedData()?

Answer 1

So I've fixed it by doing this:
In the first method, the one that actually needs the data from the API, I added this:
let trendingData = restApiManager.getLatest(pageNumber: 0, completion: { data -> Void in
let item = data[indexPath.row]
let url = NSURL(string: item.still)
let data = NSData(contentsOf: url as! URL)
if data != nil {
cell.image.image = UIImage(data:data! as Data)
}
})
The getLatest() method looks like this:
func getLatest(pageNumber: Int, completion: #escaping ([ApiItem]) -> ()) {
let urlRequest = URL(string: baseUrl + trendingUrl + String(pageNumber))
let requestedData = doRequest(url: urlRequest!, completion: { data -> Void in
// We have the data from doRequest stored in data
var requestedData = data
completion(requestedData)
})
}
And finally, the doRequest() method looks like this:
func doRequest(url: URL, completion: #escaping ([ApiItem]) -> ()){
var allItems = [ApiItem]()
URLSession.shared.dataTask(with: url) { (data, response, error) in
guard let data = data else { return }
do{
let json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as! [String: AnyObject]
let results = json["items"] as? [AnyObject]
for r in results!{
let item = ApiItem(json: r as! [String: Any])
allItems.append(item)
}
completion(allItems)
} catch let jsonError{
print("JSON error: \(jsonError)")
}
}.resume()
}

Answer 2

What I would do is use a Singleton in which I can store the Data
class DataManager:NSObject
{
static let instance = DataManager()
override private init(){}
var items:[ApiItem] = []
}
Then in your first method I would do this:
func getLatest(pageNumber: Int){
let urlRequest = URL(string: baseUrl + latestUrl + String(pageNumber))
let requestedData = doRequest(url: urlRequest!, completion: { data -> items in
// We have the data from doRequest stored in data, but now what?!
DataManager.instance.items = items
})
}
This is how I usually go about this kind of situations. There may be better options though...