using JSON data in SWIFT UI controls

Question

I need to use data from a JSON web service to update controls in a SWIFT app. I can get the data no problem, but I can't seem to access the UI controls from within the task block and I can't get the JSON to persist out of the block. I've searched around and haven't found the answer. Here's my test code. The current result is that value1Result has a value inside task, but is nil outside. Thanks in advance.

    var jsonResult:NSDictionary!
    var value1Result:String!

    let task = NSURLSession.sharedSession().dataTaskWithURL(url!) { data, response, error in
        var error: NSError?
        jsonResult = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.AllowFragments, error: &error)!
            as! Dictionary<String, AnyObject>
        println(jsonResult)

        if let value1 = jsonResult["value1"] {
            println(value1)
            value1Result = value1 as! String
            }
        }
    task.resume()

    self.textView1.text = value1Result

Asynchrone issue: stackoverflow.com/questions/31706458/swift-json-api-manager — Larme
– Larme, Commented Jul 30, 2015 at 9:12

Ashish Kakkad · Accepted Answer · 2015-07-30 09:25:48Z

2

You can use asynchronous block to update the main UI

dispatch_async(dispatch_get_main_queue()) {
    //Update your UI
}

With your code

let task = NSURLSession.sharedSession().dataTaskWithURL(url!) { data, response, error in
    var error: NSError?
    jsonResult = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.AllowFragments, error: &error)!
        as! Dictionary<String, AnyObject>
    println(jsonResult)

    if let value1 = jsonResult["value1"] {
        println(value1)
            dispatch_async(dispatch_get_main_queue()) {
                //Update your UI
                value1Result = value1 as! String
                self.yourtextview.text = value1 as! String
            }
        }
    }
task.resume()

edited Jul 30, 2015 at 9:25

answered Jul 30, 2015 at 9:17

Ashish Kakkad

23.9k13 gold badges108 silver badges140 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

beachCode Over a year ago

Ashish, could you be more specific? I tried adding the textview update line inside your example and it doesn't change the fact that value1Result is nil. Thanks

Ashish Kakkad Over a year ago

@user3026206 updated the answer. I don't know what is value1Result so, I have added the value1 as! String in text view directly.

beachCode Over a year ago

Awesome. Got it. Thanks buddy!

Ashish Kakkad Over a year ago

@user3026206 Welcome anytime :)

BaseZen · Accepted Answer · 2015-07-30 09:34:04Z

Doing proper network coding is hard. There's a lot of problems with your code both stylistically, in terms of robustness, and actual functionality. That is why networking vs. UI is always layered with a library like AFNetworking. Doing it right yourself is just too much manual labor.

Consider what it takes to check for errors properly and hand off the code properly to the UI thread:

let task = session.dataTaskWithURL(url) {
    [unowned self]
    (data: NSData?, response: NSURLResponse?, netError: NSError?) in            
    if let statusCode = (response as? NSHTTPURLResponse)?.statusCode {
        if statusCode == 200 {
            if let jsonResult = NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments, error: &error) as? Dictionary<String, AnyObject> {
                if let value1 = jsonResult["value1"] as? String {
                    dispatch_async(dispatch_get_main_queue()) {
                        self.textView1.text = value1
                    }
                }
                else {
                    println("JSON format error, key value1 not defined")
                }
            }
            else {
                println("JSON parsing error: \(error.localizedDescription)")      
            }
        else { // status code other than 200
             println("HTTP Error \(statusCode)")
        }
    }
    else { // No HTTP response available at all, couldn't hit server
        println("Network Error: \(netErr!.localizedDescription)")
    }
}

task.resume()

Collectives™ on Stack Overflow

using JSON data in SWIFT UI controls

2 Answers 2

4 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

4 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related