Pick a next item from NSArray and then start over - objective-c

Question

I need to toggle three different font sizes in the view controller for terms and conditions screen in an endless loop (13 , 15, 17..13, 15, 17..etc..). The screen is pretty simple, just text on full screen and a button in the navigation bar that when pressed, triggers and event handled in action.
The three fonts are represented by three NSString constants.
-(IBAction)toggleFontSize:(id)sender
{
if (self.currentFontIdentifier == regularFontIdentifier)
{
self.currentFontIdentifier = largeFontIdentifier;
}
else if (self.currentFontIdentifier == largeFontIdentifier)
{
self.currentFontIdentifier = smallFontIdentifier;
}
else
{
self.currentFontIdentifier = regularFontIdentifier;
}
self.termsAndConditionsTextView.font = [[BrandingManager sharedManager] fontWithIdentifier:self.currentFontIdentifier];
}
This code works (for now :)), but it's a nice Mediterranean IF yacht.I am wondering if there is some more mature approach. I already see the stakeholders changing their mind and adding a 4th font size. I want it to be manageable better, so basically once they add a new size I would only add it into some Array and that would be it.
Any ideas for a more mature algorithm?

Answer 1

Declare an instance variable for the current selected index and an array for the three fonts (small, regular and large) and try this:
-(IBAction)toggleFontSize:(id)sender {
_currentSelectedIndex = (_currentSelectedIndex + 1) % 3;
self.currentFontIdentifier = _fontIdentifiers[_currentSelectedIndex];
self.termsAndConditionsTextView.font = [[BrandingManager sharedManager] fontWithIdentifier:self.currentFontIdentifier];
}
You may not need currentFontIdentifier property since it can be obtained with _fontIdentifiers[_currentSelectedIndex]

Answer 2

You could use the methods 'indexOfObject and 'lastObject' of the NSArray class, something like:
Using an array of sizes:
NSArray *fontList = #[#"12","14","18"];
Then you could iterate through it using the indexOfObject
NSUInteger ix = [fontList indexOfObject:self.currentFontIdentifier] + 1;
if ([[fontList lastObject] isEqual:self.currentFontIdentifier])
ix=0;
self.currentFontIdentifier = [fontList objectAtIndex:ix];
or
NSUInteger ix = [fontList indexOfObject:self.currentFontIdentifier] + 1;
if (ix >= [fontList count])
ix=0;
self.currentFontIdentifier = [fontList objectAtIndex:ix];