xcode debugging terminates when i run app

When I run my app in Xcode using the simulator it runs just file until I add in the first three lines involving the text file. It gives me a message saying terminate called after throwing an instance of 'NSException'. I don't know what that means or why it only happens when I try to read in the text file and display it in the textView.

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    NSString *filePath = [[NSBundle mainBundle] pathForResource:@"textfiles/brain_01" ofType:@"txt"];//establish file path for text file
    NS开发者_开发问答String *textFile = [[NSString alloc] stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error: nil];
    textView.text = textFile;
    [super viewDidLoad];    
    fullButton.hidden = YES;
    viewLabel.hidden = YES;
}

NSException means your code has a bug in it. An exception is an error. In your case, it's probably because

NSString *textFile = [[NSString alloc] stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error: nil];

should be

NSString *textFile = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error: nil];

stringWithContentsOfFile is a class method used to make NSString -- only use alloc with init... methods.