Change index of specific char of NSString - ios

Question

I have a string, for example "Soccer". Now I want to move every "e" by lets say 2 indexes(right word?), so my string looks like this = "erSocc". This has to work with whitespace and negative/- indexes.
I came a cross with this, not perfect working, solution:
NSString* text = #"Soccer";
NSString* sign = #"c";
int index = 1;
NSMutableArray* arrayText = [[NSMutableArray alloc]init];
NSMutableArray* arraySignNewPosition = [[NSMutableArray alloc]init];
NSMutableArray* arrayOldSignPosition = [[NSMutableArray alloc]init];
for(int i=0;i<(text.length);i++)
{
[arrayText addObject:[text substringWithRange:NSMakeRange(i, 1)]];
if ([[arrayText objectAtIndex:i]isEqualToString:sign])
{
[arrayOldSignPosition addObject:[NSNumber numberWithInt:i]];
if ((i+index)>(text.length-1))
{
int indexDifference = (i+index)-(text.length);
[arraySignNewPosition addObject:[NSNumber numberWithInt:indexDifference]];
}
else
{
[arraySignNewPosition addObject:[NSNumber numberWithInt:(i+index)]];
}
}
}
for (NSNumber* number in arraySignNewPosition)
{
[arrayText insertObject:sign atIndex:number.integerValue];
if(number.integerValue-index>0)
{
[arrayText removeObjectAtIndex:(number.integerValue-index)];
}
else
{
[arrayText removeObjectAtIndex:((arrayText.count-1)+(number.integerValue-index))];
}
}
I know the code is not working perfectly, but I would like to know if this is the right way or if there are some Cocoa functions I could use to accomplish my goal. Thanks for your time.

Answer 1

You're really just getting substrings and moving them around, so you could do something like this:
- (NSString *)shiftRight:(NSUInteger)places
{
NSAssert(places > 0, #"places must be greater than 0");
NSAssert(places < [self length], #"places must be less than the length of the string");
places = [self length] - places;
NSString *start = [self substringFromIndex:places];
NSString *end = [self substringToIndex:places];
return [start stringByAppendingString:end];
}
Here's a complete code listing, with examples.