Returning JSON Data from inside loop

Question

I am trying to return the values that i get from the JSON response

    func getAsset(imageId: String) -> String{
    let url = "https://myimage.com"
    Alamofire.request(.GET, url).responseJSON { response in
        switch response.result {
        case .Success:
            if let value = response.result.value {
                dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)) {
                    let json = JSON(value)
                    let singleAsset = json["fields"]["file"]["url"].string
                    print(singleAsset)
                }
            }
        case .Failure(let error):
            print(error)
        }
    }
}

I am trying to return the value (singleAsset) but cant because i keep getting the error unresolved identifier. Ive been trying all night but cant return to value.

arturdev · Accepted Answer · 2015-12-01 14:11:20Z

1

You should use completion handlers:
See: https://thatthinginswift.com/completion-handlers/

func getAsset(imageId: String, completion: (String) -> Void) {
    let url = "https://myimage.com"
    Alamofire.request(.GET, url).responseJSON { response in
        switch response.result {
        case .Success:
            if let value = response.result.value {
                dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)) {
                    let json = JSON(value)
                    let singleAsset = json["fields"]["file"]["url"].string
                    print(singleAsset)
                    completion(singleAsset)
                }
            }
        case .Failure(let error):
            print(error)
            completion(nil);
        }
    }

Usage:

getAsset(imageId) {result in
    println("got back: \(result)")
}

edited Dec 1, 2015 at 14:11

answered Dec 1, 2015 at 13:59

arturdev

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3 Comments

Slygoth Over a year ago

Thanks this works but how do i take the value i got out the function? I want to use the output somewhere else in the code not just the function

Slygoth Over a year ago

So i want the value of results to be used elsewhere in the code.

arturdev Over a year ago

Keep that in a property

mohonish · Accepted Answer · 2015-12-01 14:08:12Z

0

Whenever you send a request to any web API endpoint, the response is never instantaneous and may take some time. That is why you're actually passing a block of code to Alamofire.request that is run whenever a response is received.

You could also pass a block as a parameter to getAsset function and execute it whenever the response is received (as pointed out by @arturdev already in his answer)

Additionally, you could also have a singleton class and implement a delegate/protocol structure that notifies your view controllers whenever there is a response.

answered Dec 1, 2015 at 14:08

mohonish

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