xCode won't allow addObject - ios

Question

absolute beginner here. I'm trying to teach myself Xcode using several different sources. My current lesson, I'm just trying to capitalize each word in a string. For some reason, I'm not given the option of using addObject, even though I've resorted to copying line for line what's in the book! Here's the code I'm using, I'm just typing it into the ViewController.m. I haven't touched the header file.
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSString *myString = #"How much wood could a woodchuck chuck";
NSArray *wordsInSentence = [myString componentsSeparatedByString:#" "];
NSLog(#"%#", wordsInSentence);
NSMutableArray *capitalizedWords = [[NSMutableArray alloc] init];
for (int word =0; word < [wordsInSentence count]; word++)
{
NSString *uncapitalizedWords = [wordsInSentence objectAtIndex:word];
NSString *capitalizedWords = [uncapitalizedWords capitalizedString];
[capitalizedWords addObject:capitalizedWords];
}
NSLog(#"%#", capitalizedWords);
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end
My problem is with
[capitalizedWords addObject:capitalizedWords];
When I begin typing, it doesn't even show addObject in the drop down box as an option, the only option I have is addObserver.
Any and all help would be much appreciated, Thanks

Answer 1

The problem is that you have two variables with the same name, capitalizedWords. One is the mutable array, the other is the string. And, thus, when you use capitalizedWords inside that for loop, it's using the string rendition. I would suggest renaming the string variable, e.g., replace:
NSString *uncapitalizedWords = [wordsInSentence objectAtIndex:word];
NSString *capitalizedWords = [uncapitalizedWords capitalizedString];
[capitalizedWords addObject:capitalizedWords];
with
NSString *uncapitalizedWord = [wordsInSentence objectAtIndex:word]; // renaming this isn't critical, but using singular case makes it more clear
NSString *capitalizedWord = [uncapitalizedWord capitalizedString]; // renaming this fixes the problem
[capitalizedWords addObject:capitalizedWord];

Answer 2

The problem is that you are naming the string the same as the array.
Try changing
NSString *capitalizedWords = [uncapitalizedWords capitalizedString];
[capitalizedWords addObject:capitalizedWords];
to:
NSString *capitalizedWordsString = [uncapitalizedWords capitalizedString];
[capitalizedWords addObject:capitalizedWordsString];
When you're declaring the string with the same name as the array you're shadowing the array and Xcode will see capitalizedWords as a string, not an array. That's why it doesn't present you with the addObject method.