Question

Hello I created a app on iOS 4.3.3 and than downloaded Xcode 4.2.1 and iOS sdk 5. It’s a navigation-based application and it has a mutable array for the tableview but it won’t create any strings for the array, so i added an object to array in the viewdidload but it is not working! So i added NSlog to the objects in my array and it says null! What should i do?

Here’s the viewdidload:

    - (void)viewDidLoad
    {
    [super viewDidLoad];
    self.soldc = [NSMutableArray arrayWithCapacity:0];
    self.color = [NSMutableArray arrayWithCapacity:0];
    appdelegate = (yard_sale_managerAppDelegate *)[[UIApplication sharedApplication]          delegate];
    appdelegate.object = self;
    NSMutableArray *loadi = [[NSMutableArray alloc]initWithCapacity:0];
    self.items = loadi;
    self.sold = [NSMutableArray arrayWithCapacity:0];
    self.prices = [NSMutableArray arrayWithCapacity:0];

    alert = [[UIAlertView alloc] initWithTitle:@"Add product" message:@"Enter your   product name and price." delegate:self cancelButtonTitle:@"Add" otherButtonTitles:@"Cancel",   nil];
    [alert addTextFieldWithValue:@"" label:@"name"];
    [alert addTextFieldWithValue:@"" label:@"price"];
    add = [alert textFieldAtIndex:0];
    add.keyboardType = UIKeyboardTypeAlphabet;
    add.keyboardAppearance = UIKeyboardAppearanceAlert;
    add.autocapitalizationType = UITextAutocapitalizationTypeWords;
    add.autocorrectionType = UITextAutocorrectionTypeNo;
    add2 = [alert textFieldAtIndex:1];
    add2.keyboardType = UIKeyboardTypeNumberPad;
    add2.keyboardAppearance = UIKeyboardAppearanceAlert;
    add2.autocapitalizationType = UITextAutocapitalizationTypeWords;
    add2.autocorrectionType = UITextAutocorrectionTypeNo;
    NSLog(@"%i", [color count]);
    alert.tag=1;
    self.resa = [[UIAlertView alloc] initWithTitle:@"Sale results" message:@"temple" delegate:self cancelButtonTitle:@"Close" otherButtonTitles: nil];
    self.items = [NSMutableArray arrayWithContentsOfFile:[self itemsp]];
    self.prices = [NSMutableArray arrayWithContentsOfFile:[self pricesp]];
    self.sold = [NSMutableArray arrayWithContentsOfFile:[self soldp]];
    self.soldc = [NSMutableArray arrayWithContentsOfFile:[self soldcp]];
    self.color = [NSMutableArray arrayWithContentsOfFile:[self colorsp]];
    if ([self.soldc count]==0) {

    }
    //self.soldc = [NSMutableArray arrayWithContentsOfFile:[self soldcp]];
    self.color = [NSMutableArray arrayWithContentsOfFile:[self colorsp]];
    [loadi release];
    self.resa.tag = 2;
    [self.items addObject:@"chair"];   
    [self.prices addObject:@"30"];
    [self.color addObject:@"0"];
    NSLog(@"%@",self.items);
}

If you need more information tell me!
This is the log:

2012-01-08 21:31:13.409 yard sale manager[1152:f803] 0
2012-01-08 21:31:13.411 yard sale manager[1152:f803] (null)

edit: read this its important!!!!!
a lot of people didn’t notice that piece of code:
[self.items addObject:@”chair”];
[self.prices addObject:@”30″];
[self.color addObject:@”0″];
NSLog(@”%@”,self.items);

Answer 1

This line

self.color = [NSMutableArray arrayWithCapacity:0];

instantiates and assigns an empty array, you then do not add anything to it therefore the 0 count.

Then this line

self.items = [NSMutableArray arrayWithContentsOfFile:[self itemsp]];

is probably the cause. Does [self itemsp] return a valid file path that points to a file that can be parsed into an NSArray.

There are also a lot of other issues with this code.

---

Update

This line

self.items = [NSMutableArray arrayWithContentsOfFile:[self itemsp]];

must be returning nil.

Confirm by adding this line straight after it

NSLog(@"%@", self.items);

How can I make this assumption

The reason I am making this assumption is because you are getting (null). When you call addObject: on nil you will get nil returned and it is a no-op. As you can see from this snippet

NSMutableArray *myArray = nil;

[myArray addObject:@"Test"];

NSLog(@"%@", myArray);

// => 2012-01-08 20:54:04.708 Untitled[4199:707] (null)

Just because myArray holds a pointer to an NSMutableArray it does not mean that you actually have one.

Therefore the last time you assign to self.items is in:

self.items = [NSMutableArray arrayWithContentsOfFile:[self itemsp]];

which means [NSMutableArray arrayWithContentsOfFile:[self itemsp]] is returning nil