I have an array with following elements in ViewDidLoad method 
inputArray = [NSMutableArray arrayWithObjects:@"car", @"bus", @"helicopter", @"cruiz", @"bike", @"jeep", nil];
I have another UITextField for searching the elements .So once i type some thing in UITextField i want  to check whether that string is present in "inputArray" or not.If it is not matching with elements  in inputArray then  remove the corresponding elements from inputArray . 
 for (NSString* item in inputArray)
   {
        if ([item rangeOfString:s].location == NSNotFound) 
        {
            [inputArray removeObjectIdenticalTo:item];//--> Shows Exception
            NSLog(@"Contains :%@",containsAnother);
        }
  }
but this code shows exception , something related to "removeobject:"
Exception :
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSCFConstantString rangeOfString:options:range:locale:]: nil argument'
*** First throw call stack:
`
                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]]; 
                        You can use the following code
for (int i=0;i<[inputArray count]; i++) {
        NSString *item = [inputArray objectAtIndex:i];
        if ([item rangeOfString:s].location == NSNotFound) {
            [inputArray removeObject:item];
            i--;
        }
    }
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