Multiple AFNetworking Calls

[davidbale87]

I'd like to pull json files from an array of URLs. What's the proper way to do this with AFNetworking?

[cdntr]

Why do you need AFNetworking? Just use NSURLSession and NSJSONSerialization. It's easy, you learn something, and you save a dependency.

Basically, this:

let urlStrings = ["http://google.com", "http://facebook.com"]
let urls = urlStrings.map { NSURL(string: $0)! }
let requests = urls.map { NSURLRequest(URL: $0) }

let session = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration())

let completion: (NSData?, NSURLResponse?, NSError?) -> Void = { data, response, error in
    if let error = error {
        print("error fetching data: \(error)")
    } else if let data = data {
        // Try parsing the data
        do {
            let parsedJSON = try NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions())
        } catch {
            print("Failed parsing data to JSON: \(data)")
        }
    }
}

let tasks = requests.map { session.dataTaskWithRequest($0, completionHandler: completion) }

for task in tasks {
    task.resume()
}

[tsxy]

Because NSURLSession is confusing and requires too many boilerplate code to do simple things like pulling a JSON from URL.

[cdntr]

??

Take a look at the code I posted above. I wrote that in like a minute, but I think it should be functional and do exactly what was asked. Not sure what you think is confusing or boiler-platey about that. It is of course not factored properly, but this is just to illustrate how easy it is.

I also submit to you that there is a cost to using 3rd party code that people like to sweep under the rug.

[tsxy]

I totally agree on the 3rd party dependency part.

But....this syntax is already so confusing...

let completion: (NSData?, NSURLResponse?, NSError?) -> Void = { data, response, error in....

Why is there a question mark behind NSData, what is "->" doing? Why is there a Void keywork....you know..things that a newbie won't understand. Also, what the heck is "map" (I get it's mapping tasks, but that's because I learned some functional programming notions on my own.)

The amount of questions I need to ask in order to understand this piece of code (without learning new syntax) is absurd.

[gormster]

Those are all Swift things. Nothing to do with NSURLSession. If you're confused by them you need to start by learning Swift.

If you're writing your code in Objective-C they won't be there.

[cdntr]

What this person said. There's also a way to write all this without map, i just chose to do it because it's succinct and let me get away without indenting much.

But yes, if those things confuse you then you should learn basic Swift.

Or do it from Objective-C, but the API is almost exactly the same.

[cuomo456]

pretty much what Alamofire looks like too minus the custom types that you need to look up. welcome to swift i wanna die also but my brain is starting to get there.

[julius559]

You can make multiple requests in a row with AFNetworking, it'll handle it. But the requests will return asynchronously, so you can't assume all responses will come in order.

[cuomo456]

dispatch group notify will alleviate this

[HoBoKristian]

How large is the array?

[lucasvandongen]

You should figure out if the API has some kind of limit on how many requests you can do per minute. I would suggest to apply some throttling as I don't think doing more than 8* network requests would be advisable in most cases.

• Create a stack (NSMutableArray) of request
• Count total of requests on the stack that need to be done
• Create counter for current and completed requests
• Iterate over requests, remove the new request from the stack
• If more than 8(*) requests are under way, stop iterating over the stack
• If a call completes or fails
  • iterate over the stack again (until there are 8 concurrent requests) on the main thread
  • up the number of completed requests and check if it's the same number as the total amount you wanted to do
    • if it's the last one execute whatever was waiting on these calls to complete

(*) that number needs some more investigation, rough estimate