Cannot Find File with NSFileManager - objective-c

Question

Im trying to find a file with NSFileManager. The file exists but my path is never correct no matter how its phrased. The code I'm using is below. Why is NSFileManager not finding the file?
NSString *myFile = #"file1658.pdf";
NSFileManager *fileManager = [NSFileManager defaultManager];
if ([fileManager fileExistsAtPath:myFile]) {
NSLog(#"good");
}

Answer 1

MyFile is not a full path (e.g., "/Users/Joe/Documents/file1658.pdf"), so NSFileManager is looking for it in the current working directory. You can see what that is with -[NSFileManager currentDirectoryPath].
You need to either include the full path to the file as part of myFile, or set the proper working directory with -[NSFileManager changeCurrentDirectoryPath:].
// If myFile is in "/Users/joe/Documents"...
[fileManager changeCurrentDirectoryPath:#"/Users/joe/Documents"];
if ([fileManager fileExistsAtPath:myFile]) {
NSLog(#"good");
}

Answer 2

Apple tries hard to get you to put your files in sensible places. The file my exist, but you will have to either give the full path, e.g. /Users/user2759189/file1658.pdf or specify what folder it is in by other means.
App bundle
If the file is in your app bundle (for example, you have added it using "Add files to [project]" in XCode) you can get its path by something like:
NSString *myFile = [[NSBundle mainBundle] pathForResource:#"file1658" ofType:#"pdf"];
Search paths
You can look for user documents in a civilised manner by using the foundation function NSSearchPathForDirectoriesInDomains and some built in constants. If the file is in the user's Documents folder, for example, you can use something like:
NSString *documentsPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *myFile = [documentsPath stringByAppendingPathComponent:#"file1658.pdf"];