Question

I have a string whose each character is am storing in a char like

char currentLetter;

When the loop runs for i=0 the first letter of the sting is copied to currentLetter. and on i=1 the second letter is copied.
However what I want i to save each of the string index of a particular letter.

How can I do that?

Answer 1

NSString *str = @"Hello World";
NSMutableIndexSet *indexSet = [NSMutableIndexSet indexSet];

for (NSUInteger i = 0; i < [str length]; i++)
{
    if ([str characterAtIndex:i] == 'o')
        [indexSet addIndex:i];
}

// indexSet now contains all the indexes of the letter 'o' in "str"
// which should be 4 and 7.

The NSIndexSet and NSMutableIndexSet classes are useful for storing indexes because they provide other methods for manipulating and efficiently dealing with indexes.