Remove object from NSMutableArray?

In fast enumeration you can NOT modify the collection.

The enumerator object becomes constant and immutable.

If you want to do updation on the array

You should like this :

NSMutableArray *inputArray = [NSMutableArray arrayWithObjects:@"car", @"bus", @"helicopter", @"cruiz", @"bike", @"jeep", nil];
NSString *s=@"bus";

for (int i=inputArray.count-1; i>-1; i--) {
    NSString *item = [inputArray objectAtIndex:i];
    if ([item rangeOfString:s].location == NSNotFound) {
        [inputArray removeObject:item];
    }
}

EDIT:

The above works similar as this :

NSArray *array=[inputArray filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"SELF CONTAINS[c] %@",s]]; 

That needs to be an NSMutableArray. You can't modify an NSArray once created (except to start all over).

Change this:

inputArray = [NSArray arrayWithObjects:@"car", @"bus", @"helicopter", @"cruiz", @"bike", @"jeep", nil];

to this:

inputArray = [NSMutableArray arrayWithObjects:@"car", @"bus", @"helicopter", @"cruiz", @"bike", @"jeep", nil];

and also change the property to NSMutableArray also:

@property(nonatomic, strong) NSMutableArray *inputArray;

The s in your question is probably nil. So your are getting the exception.Please check that out.

Use following Code. (This Code is use for filter Array base on input string/text of UITextField )

Take Two NSMutableArray and add one array to another array in ViewDidLoad method such like,

self.listOfTemArray = [[NSMutableArray alloc] init]; // array no - 1
self.ItemOfMainArray = [[NSMutableArray alloc] initWithObjects:@"YorArrayList", nil]; // array no - 2 

[self.listOfTemArray addObjectsFromArray:self.ItemOfMainArray]; // add 2array to 1 array

And Write following delegate Method of UISearchBar

- (BOOL) textFieldDidChange:(UITextField *)textField
 {
        NSString *name = @"";
        NSString *firstLetter = @"";

    if (self.listOfTemArray.count > 0)
         [self.listOfTemArray removeAllObjects];

        if ([searchText length] > 0)
        {
                for (int i = 0; i < [self.ItemOfMainArray count] ; i = i+1)
                {
                        name = [self.ItemOfMainArray objectAtIndex:i];

                        if (name.length >= searchText.length)
                        {
                                firstLetter = [name substringWithRange:NSMakeRange(0, [searchText length])];
                                //NSLog(@"%@",firstLetter);

                                if( [firstLetter caseInsensitiveCompare:searchText] == NSOrderedSame )
                                {
                                    // strings are equal except for possibly case
                                    [self.listOfTemArray addObject: [self.ItemOfMainArray objectAtIndex:i]];
                                    NSLog(@"=========> %@",self.listOfTemArray);
                                }
                         }
                 }
         }
         else
         {
             [self.listOfTemArray addObjectsFromArray:self.ItemOfMainArray ];
         }

        [self.tblView reloadData];
}

}

Output Show in your Console.

As others have said you can't mutate an array while it is being enumerated. The easiest way to do what you want and keep the convenience of fast enumeration is to copy the array.

for (NSString* item in [inputArray copy]) {
   ...
}

This is a clean solution that I like to use. You define a NSArray category to extend it and create a map method. This method creates a new NSArray based on what you return within your block:

@interface NSArray (BlockExtensions)
/*! 
 Invokes block once for each element of self, returning a new array containing the
 values returned by the block.
 */
- (NSArray *)map:(id (^)(id obj))block;

@end

@implementation NSArray (BlockExtensions)

- (NSArray *)map:(id (^)(id obj))block
{
    return [self mapWithOptions:0 usingBlock:^id(id obj, NSUInteger idx) {
        return block(obj);
    }];
} 

- (NSArray *)mapWithOptions:(NSEnumerationOptions)options usingBlock:(id (^)(id obj, NSUInteger idx))block
{
    NSMutableArray *array = [NSMutableArray arrayWithCapacity:[self count]];
    [self enumerateObjectsWithOptions:options usingBlock:^(id obj, NSUInteger idx, BOOL *stop)     {

        id newobj = block? block(obj, idx) : obj;
        if (newobj)
            [array addObject:newobj];
    }];
    return array;
}
    @end

The block will be called once for every item in your original array, passing this object as a parameter:

NSArray *newArray = [inputArray map:^id(NSString *item) {
    if ([item rangeOfString:s].location == NSNotFound) {
        return item;
    }
    return nil;
}];

newArray will contain your filtered out items!

+1 to Anoop for pointing out that you can use filteredArrayUsingPredicate. Thus, if you wanted to create a new array based upon the matches in inputArray, you could also use something like:

NSArray *matchingArray = [inputArray filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"SELF contains[c] %@", s]];

Alternatively, given that inputArray is a NSMutableArray you can simply filter the array with this single line:

[inputArray filterUsingPredicate:[NSPredicate predicateWithFormat:@"SELF contains[c] %@", s]];

Or, if you like blocks:

[inputArray filterUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(id evaluatedObject, NSDictionary *bindings) {
    return ([evaluatedObject rangeOfString:s].location != NSNotFound);
}]];