NSTimer crashing my application - objective-c

Question

So I have an application which uses an NSTimer. The problem is that when the NSTimer runs, my application will crash with EXC_BAD_ACCESS. I only just started with objective-c so I don't know how to properly debug it. If I thought call the -(void)logIn{} with [self logIn]; the application will work.
My code:
.h
#interface DJ_WAppDelegate : NSObject {
NSTimer *loginTimer;
}
-(void)logIn;
#end
.m
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
[self logIn]; // this works
loginTimer = [NSTimer scheduledTimerWithTimeInterval:5.0 target:self selector:#selector(logIn) userInfo:nil repeats:YES]; // this fails
}
- (void)logIn {
NSLog(#"Logging in...");
// if I comment out these 2 lines it works with the NSTimer!?... (I've would have more code below)
NSURL *loginConn = [NSURL URLWithString:[NSString stringWithFormat:#"some-website.com"]];
NSInteger loginReturn = [[NSString stringWithContentsOfURL:loginConn encoding:NSASCIIStringEncoding error:nil] intValue];
// when "loginReturn" return "OK" the timer (loginTimer) will be stopped with: [loginTimer invalidate];
// more code would be below... (which works!)
}
So the problem is with the NSURL it think.
Thanks for helping.
EDIT 1:
Here's the crash stack:
EException Type: EXC_BAD_ACCESS (SIGBUS)
Exception Codes: KERN_PROTECTION_FAILURE at 0x0000000000000020
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Application Specific Information:
objc_msgSend() selector name: respondsToSelector:
Thread 0 Crashed: Dispatch queue: com.apple.main-thread
0 libobjc.A.dylib 0x9603bed7 objc_msgSend + 23
1 com.apple.CoreFoundation 0x922ed5f2 _CFStringAppendFormatAndArgumentsAux + 3138
2 com.apple.CoreFoundation 0x922ec979 _CFStringCreateWithFormatAndArgumentsAux + 105
3 com.apple.Foundation 0x9656ebfb -[NSPlaceholderString initWithFormat:locale:arguments:] + 163
4 com.apple.Foundation 0x9656eaae +[NSString stringWithFormat:] + 88
5 com.who.DJ-W 0x00001d56 -[DJ_WAppDelegate logIn] + 116 (DJ_WAppDelegate.m:108)
6 com.apple.Foundation 0x965b08d4 __NSFireTimer + 141
7 com.apple.CoreFoundation 0x922ffadb __CFRunLoopRun + 8059
8 com.apple.CoreFoundation 0x922fd464 CFRunLoopRunSpecific + 452
9 com.apple.CoreFoundation 0x922fd291 CFRunLoopRunInMode + 97
10 com.apple.HIToolbox 0x91646e04 RunCurrentEventLoopInMode + 392
11 com.apple.HIToolbox 0x91646bb9 ReceiveNextEventCommon + 354
12 com.apple.HIToolbox 0x91646a3e BlockUntilNextEventMatchingListInMode + 81
13 com.apple.AppKit 0x9265378d _DPSNextEvent + 847
14 com.apple.AppKit 0x92652fce -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 156
15 com.apple.AppKit 0x92615247 -[NSApplication run] + 821
16 com.apple.AppKit 0x9260d2d9 NSApplicationMain + 574
17 com.who.DJ-W 0x00001c92 start + 54
hope this helps... to find the error
EDIT 2:
With the Zombie Mode on I get this: *** -[CFString respondsToSelector:]: message sent to deallocated instance 0x46d550 I hope this helps.
EDIT 3:
To Ball: Here is the original URL (took away the domain here) /DJW/work.php?user=iBlackbirdi&udid=00000000-0000-1000-80005&key=660e5744e&cmd=slocau&type=get

Answer 1

There are several problems here:
djwLog is a class method so you should call it on the class not the instance
like this: [[self class] djwLog:#"foo bar"]
The URLFromString: method needs the string to contain a valid URL as specified by RFC 1808. Something along the lines of [NSURL URLFromString:#"http://example.com/foo"]
stringWithContentsOfURL:url… is a syncornous method. Unless you have this code running in a separate thread you should not use this. Look at NSURLConnection for a class to asynchronously load data from a URL. Using synchronized calls for this is a bad idea. Always.
intValue returns a signed integer. To get a NSInteger use integerValue. Also if you use stringWithContentsOfURL make sure to check if it's result is nil before calling
integerValue otherwise you might get a result of 0 if the URL call failed or did not return data. A real parser for the API you are calling would be a good idea in any case.

Answer 2

You're calling a class method as if it was an instance method:
[self djwLog:#"Logging in..."];
Since there is no instance-method named djwLog the application crashes. You should either call NSLog directly, make it an instance-method - or preferably make a macro for logging:
#ifdef DEBUG
# define DLog(...) NSLog(#"%s %#", __PRETTY_FUNCTION__, [NSString stringWithFormat:__VA_ARGS__])
#else
# define DLog(...) do { } while (0)
#endif
If you instead of NSLog write DLog - it will only be logging when DEBUG-flag has been defined. In addition to this, it will log the origin of the log message - so you can see which class/method the log entry came from.