how to ask an array if an object is contained?

Question

how can i ask an array if it contains an item and if it does it to [[NSArray alloc] initWithObjects:@"those objects" automatically. this is my fav .h

@interface FavoriteViewController : UITableViewController {
    NSMutableArray *favoritesArray;
    NSMutableArray *didContain;
}
@property (nonatomic, retain) NSMutableArray *favoritesArray;

@property (nonatomic, retain) NSMutableArray *didContain;

this is the .m

 favoritesArray = [[NSMutableArray alloc]init];
didContain = [[NSMutableArray alloc]init];

if 
([favoritesArray containsObject:@"one"])
{

    [didContain addObject:@"one"];
}

and in the detail view controller.m i have this code

[[NSMutableArray alloc] init];
[favoritesArray addObject: @"one"];

i get the table to work however nothing shows up....

Answer 1

  NSArray *yourArray = [[NSArray alloc] initWithObjects:@"Hello", @"World", nil];
  NSMutableArray *didContain = [[NSArray alloc] init];


  if([yourArray contains: @"Hello"])
{
        [didContain addObject:@"Hello"];
}

or

  NSArray *yourArray = [[NSArray alloc] initWithObjects:@"Hello", @"World", nil];
  NSMutableArray *didContain = [[NSArray alloc] init];

  [didContain addObject: [yourArray objectAtIndex:[yourArray indexOfObject:@"Hello"]];

All of this and more is readily available in the apple docs. Please do some google searching first next time. Good luck hope this helps.

Answer 2

Use filteredArrayUsingPredicate: See NSArray Class Reference and Predicate Programming Guide

It appears that you are trying to use an uninitialized property in your detail view controller.

Normally, you initialize properties in your init: or viewDidLoad method implementations then before presenting the view in your parent view controller, set the property using the property accessors

This line:

// DetailViewController.m initializer code
[[NSMutableArray alloc] init]; // returned object is not used

Should be:

 favoritesArray = [[NSMutableArray alloc] init]; // view controller initialization code

Instead of calling this:

 [favoritesArray addObject:@"one"]; 

After you create your detailViewController set the favoritesArray with the filtered array

// FavoriteViewController.m 
MyDetailViewController *dvc = [[MyDetailViewController alloc] initWithNibName:@"MyDetailViewController" bundle:nil];

// populate the array
[dvc setFavoritesArray:didContain];

// Assuming you are using a navigation controller

[navigationController pushViewController:dvc animated:YES];
[dvc release];