How to call rest web service from swift

Question

I am trying to follow a tutorial - which failed and having found some code on stack over flow Make REST API call in Swift decided to try this approach instead. The following code is a copy and paste (I know!) with a change of URL yet I seem to be getting an error printed to the console rather than the JSON - the error being largely unhelpful - 0x0000000000000000

The JSON appears to print to the browser window so I am not fully sure what might be wrong with this approach? Please could someone provide some help as to why this might not be working?

Thanks

    var url : String = "http://www.flickr.com/services/rest/?method=flickr.test.echo&format=json&api_key=d6e995dee02d313a28ed4b799a09b869"
    var request : NSMutableURLRequest = NSMutableURLRequest()
    request.URL = NSURL(string: url)
    request.HTTPMethod = "GET"

    NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue(), completionHandler:{ (response:NSURLResponse!, data: NSData!, error: NSError!) -> Void in
        var error: AutoreleasingUnsafeMutablePointer<NSError?> = nil
        let jsonResult: NSDictionary! = NSJSONSerialization.JSONObjectWithData(data, options:NSJSONReadingOptions.MutableContainers, error: error) as? NSDictionary

        if (jsonResult != nil) {
            println(jsonResult);
        } else {
            // couldn't load JSON, look at error
            println(error);
        }
    })

You're not passing that error object correctly. Define it as var error: NSError? and pass it with ..., error: &error); Swift will do the converting back and forth to a pointer for you. See Adopting Cocoa Design Patterns. — Mike S
– Mike S, Commented Oct 3, 2014 at 14:40

abinop · Accepted Answer · 2014-10-03 14:16:57Z

2

The problem is that the call returns data in JSONP not JSON

Your code would work ok if tested with a correct JSON like http://ip.jsontest.com

To make it work with Flickr you have to modify it as follows:

var json_str:NSString = NSString(data: data, encoding: NSUTF8StringEncoding)


json_str = json_str.substringFromIndex(14)
json_str = json_str.substringToIndex(json_str.length-1)

let new_data:NSData = json_str.dataUsingEncoding(NSUTF8StringEncoding)!


var error: AutoreleasingUnsafeMutablePointer<NSError?> = nil
let jsonResult: NSDictionary! = NSJSONSerialization.JSONObjectWithData(new_data, options:NSJSONReadingOptions.MutableContainers, error: error) as? NSDictionary

if (jsonResult != nil) {
    println(jsonResult);
} else {
    // couldn't load JSON, look at error
    println(error);
}

answered Oct 3, 2014 at 14:16

abinop

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2 Comments

Mike S Over a year ago

You can also tell the Flickr API to send back straight JSON instead of JSONP by adding the parameter nojsoncallback=1 to the URL.

ChainFuse Over a year ago

@abinop can you make this example a bit more clear and integrate it with his code? That'd be extremely helpful. Thank you.

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