NSTextTab - Correct use of "options"

Question

I have recently begun using Xcode 7 and have gotten what appears to be a common warning:

Null passed to a callee that requires a non-null argument

I understand what it is telling me, but I am not sure what the correct solution is for my particular issue. Here's the line where the warning is occurring:

NSTextTab *tab = [[NSTextTab alloc] 
                     initWithTextAlignment:NSTextAlignmentLeft 
                                  location:10.0f
                                   options:nil];

Now, looking into Matt Neuberg's example of this in his "Programming iOS 8" book (posted on GitHub), I see the following:

let s = "Onions\t$2.34\nPeppers\t$15.2\n"
let mas = NSMutableAttributedString(string:s, attributes:[
// lines omitted...
let terms = NSTextTab.columnTerminatorsForLocale(NSLocale.currentLocale())
let tab = NSTextTab(textAlignment:.Right, location:170, options:[NSTabColumnTerminatorsAttributeName:terms])
// lines omitted
self.tv.attributedText = mas

From what I can tell, this is setting up the text so that the decimal points in the strings are what get aligned. Great. Useful. Not what I need. I'm just trying to have a tab on the left-hand side give a specific and consistent indentation.

To "fix" my code (i.e., get the warning to disappear), I've changed my code to this:

NSTextTab *tab = [[NSTextTab alloc] initWithTextAlignment:NSTextAlignmentLeft location:10.0f options:[NSDictionary dictionary]];

This appears to work, but it feels like a super-kludgy work-around. Is my understanding of NSTextTab mistaken? What's the right way to fix this?

Answer 1

The only option listed in the documentation for initWithTextAlignment:location:options: is NSTabColumnTerminatorsAttributeName and it is optional.

The options: parameter is marked nonnull in the NSParagraphStyle.h header file by the use of the NS_ASSUME_NONNULL_BEGIN/END macros.

Combine those two facts, and your solution of passing an empty NSDictionary is the proper way to resolve the compiler warning.