Segue not working? - ios

Question

I'm building an app around the Feedly API. So, in the UIWebView used to login, I use the following code:
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
NSString *URLString = [[request URL] absoluteString];
NSString *urlStart = [URLString substringToIndex:23];
if ([urlStart isEqualToString:#"http://localhost/?code="])
{
NSString *haystack = request.URL.absoluteString;
[self useURL:haystack];
}
return YES;
}
As you can see, this calls a method useURL:
- (void)useURL:(NSString *)haystack {
NSString *prefix = #"http://localhost/?code=";
NSString *suffix = #"&state=";suffix!
NSRange needleRange = NSMakeRange(prefix.length,
haystack.length - prefix.length - suffix.length);
NSString *needle = [haystack substringWithRange:needleRange];
NSLog(#"needle: %#", needle);
NSString *valueToSave = needle;
[[NSUserDefaults standardUserDefaults] setObject:valueToSave forKey:#"AuthCode"];
[[NSUserDefaults standardUserDefaults] synchronize];
NSString *client_id = #"id";
NSString *client_secret = #"secret";
NSString *redirect_uri = #"http://localhost";
NSString *state = #"";
NSString *grant_type = #"authorization_code";
NSInteger success = 0;
#try {
NSString *post =[[NSString alloc] initWithFormat:#"code=%#&client_id=%#&client_secret=%#&redirect_uri=%#&state=%#&grant_type=%#",needle,client_id,client_secret,redirect_uri,state,grant_type];
NSLog(#"PostData: %#",post);
NSURL *url=[NSURL URLWithString:#"https://cloud.feedly.com/v3/auth/token"];
NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
NSString *postLength = [NSString stringWithFormat:#"%lu", (unsigned long)[postData length]];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
[request setURL:url];
[request setHTTPMethod:#"POST"];
[request setValue:postLength forHTTPHeaderField:#"Content-Length"];
[request setValue:#"application/json" forHTTPHeaderField:#"Accept"];
[request setValue:#"application/x-www-form-urlencoded" forHTTPHeaderField:#"Content-Type"];
[request setHTTPBody:postData];
//[NSURLRequest setAllowsAnyHTTPSCertificate:YES forHost:[url host]];
NSError *error = [[NSError alloc] init];
NSHTTPURLResponse *response = nil;
NSData *urlData=[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
NSLog(#"Response code: %ld", (long)[response statusCode]);
if ([response statusCode] >= 200 && [response statusCode] < 300)
{
NSString *responseData = [[NSString alloc]initWithData:urlData encoding:NSUTF8StringEncoding];
NSLog(#"Response ==> %#", responseData);
NSError *error = nil;
NSDictionary *jsonData = [NSJSONSerialization
JSONObjectWithData:urlData
options:NSJSONReadingMutableContainers
error:&error];
NSString *accessToken = jsonData[#"access_token"];
NSString *refreshToken = jsonData[#"refresh_token"];
//[self performSegueWithIdentifier:#"presentNewView" sender:self];
NewViewController *newView = [[NewViewController alloc] init];
[self presentViewController:newView animated:NO completion:nil];
} else {
NSLog(#"Failed.");
}
}
#catch (NSException * e) {
NSLog(#"Exception: %#", e);
}
}
Most of it works fine up until the part where the next view should come in. I tried it with a segue and I tried the way as can be seen here, but both keep throwing Exception: *** -[NSURL initFileURLWithPath:]: nil string parameter
What am I doing wrong here?

Answer 1

As your error message states, you have a nil string. You can use breakpoints inside of the class and the LLDB to print the value of said string throughout its lifecycle, using po stringName in the debugger. Find where it looses the value, and you have your answer. Here are some helpful links to help you do this quickly if you're new to LLDB or breakpoints:
Breakpoints Guide
LLDB Commands
If you're more comfortable with using NSLog, placing them in the objects life cycle could be helpful as well, but I would go with the first recommendation.