Why NSURLErrorDomain -1000 (bad URL) for specific NSURLs only? - objective-c

Question

I looked through all the relevant questions I could find (search: "NSURLErrorDomain -1000"), and couldn't find a solution. Maybe somebody eagle-eyed could help me.
I'm making calls from iOS 6 to the Instagram API (but the parts that work, did so already in iOS 5.1). I'm using Koolistov's NSURL+PathParameters.h as a helper, and my understanding is that it does indeed escape everything that is necessary in the URL.
Some preliminaries:
NSDictionary *parameters = nil;
NSURL *URL = [NSURL URLWithString:#"https://api.instagram.com/"];
parameters = [NSDictionary dictionaryWithObjectsAndKeys:
INSTAGRAM_CLIENT_ID, #"client_id", nil];
URL = [URL URLByReplacingPathWithPath:#"/v1/tags/awesome/media/recent"];
URL = [URL URLByAppendingParameters:parameters];
(INSTAGRAM_CLIENT_ID is a macro that contains my app's client ID.)
This URL works as expected.
However, the URL constructed as follows gives me NSURLErrorDomain code = -1000 consistently (on device and on both iPhone 5.1 and 6.0 simulators):
double latitude = 48.858844;
double longitude = 2.294351;
parameters = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithDouble:latitude], #"lat",
[NSNumber numberWithDouble:longitude], #"lng",
[NSNumber numberWithInt:2000], #"distance",
INSTAGRAM_CLIENT_ID, #"client_id",
nil];
URL = [URL URLByReplacingPathWithPath:#"/v1/media/search"];
URL = [URL URLByAppendingParameters:parameters];
I then create an NSURLRequest:
NSURLRequest *req = [NSURLRequest requestWithURL:URL];
If I print out the URL from the NSURLRequest, it seems quite OK:
https://api.instagram.com/v1/media/search?client_id=REDACTED&distance=2000&lat=48.858844&lng=2.294351
I'm using MyDownloader from Matt Neuburg's Programming iOS 5, Chapter 37. I create an instance of MyDownloaderand pass it the NSURLRequest:
MyDownloader *downloader = [[MyDownloader alloc] initWithRequest:req];
Accoding to RFC 3986, underscores or dots don't need to be escaped, I don't see anything else to be escaped, and NSURL+PathParameters.h should handle escaping anyway. So what is going on here? What am I missing?
To add to the weirdness, also this even simpler way of constructing the URL gives the same error:
parameters = [NSDictionary dictionaryWithObjectsAndKeys:
INSTAGRAM_CLIENT_ID, #"client_id", nil];
URL = [URL URLByReplacingPathWithPath:#"/v1/media/popular"];
It also looks OK:
https://api.instagram.com/v1/media/popular?client_id=REDACTED
All of these URLs work in the Instagram API console and directly in Safari. These API calls don't need OAuth authentication, just the client ID.
I would be greatful if somebody could point out what the problem is.
EDIT: encoded the lat and lng values with:
[[[NSNumber numberWithDouble:latitude] stringValue]
stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]
No change in URL or behavior. But when I replace the dots with literal %2E's, the path helper encodes the percent sign, resulting in %252E...

Answer 1

Solved. There was nothing wrong with the URLs shown above. The problem was with surrounding code. I'm answering my own question so that someone working with the Instagram API might benefit from the answer.
It turns out that the /v1/tags/tagname/media/recent endpoint of the API returns a pagination object in the JSON response, but the /v1/media/search and /v1/media/popular do not. From inside that object you can find the URL to the next batch of photos, in a value called next_url.
Because I hadn't read the documentation properly (and it was a little confusing in places), and because the different Instagram API endpoints work differently, my code expected to find the next_url value in all those cases. So the "bad URL" I was getting from NSURLConnection was referring to the second connection, and not the initial URL. Since I did not realize there is no pagination in the two other cases, I assumed that the problem must be in the initial URL.