String Formatting

[charlieMonroe]

Thanks for fixing the precision formatting, however, there are more format modifiers:

@implementation ABC

-(void)xy {
    NSString *statementID = [NSString stringWithFormat:@"%05li", (unsigned long)[file bankStatementID]];
}

@end

Currently gives:

class ABC {
    func xy() {
        let statementID = "%05li"
    }
}

Discarding the formatting completely. As mentioned before, I believe there should be a check of the number of formatting tokens in the format string and the number of arguments of the formatting method - and if they don't match, either throw an error, or fall back to the String(format: ...) initializer.

[drkameleon]

Hmm... I know what you mean...

Basically, the regex matching "precision" currently is: %[0-9]?\.?[0-9]+[fg] (meaning: which are going to fall bac to the String(format: ...) initializer.

Suggestions? (Apart from the example you mentioned I mean...)

[charlieMonroe]

Well, this isn't precision per sea, it's a padding formatting. Generally speaking C-style formatting can get really wild :)

See http://stackoverflow.com/a/29403060/1800936

According to this person, the regex for a placeholder is pretty insane.

For now, though, I believe that changing the regex to %[0-9.]+l?[fgid] should be sufficient. But this is based on my needs - there certainly are people using much more complex formatting.

I can't see into your code, so I don't know if it's possible, but when converting such an expression, I'd suggest:

• match very generically %[0-9a-zA-Z.]+ - notice the upper case letters included, since %02X will convert the number into an upper-case hex (e.g. 2F), which is often used.
• if you get matches that cannot be handled directly by Swift string interpolation -> fall back on String(format: ...).
• it's always better to be on the safe side - it's better to use the String(format: ...) initializer when it doesn't have to be used, rather than the opposite, thus creating a code that does something different.

[drkameleon]

Well, this isn't precision per sea, it's a padding formatting.

Well, true... lol.

---

Thanks a lot for your input. I'm looking into it right now. ;-)

[drkameleon]

Marking the issue as fixed of the upcoming 2.4 - but I'll guess we'll have to re-visit. But... what can I say... that's what I'm here for... ;-)

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Example:

NSString *statementID = [NSString stringWithFormat:@"%05li", (unsigned long)[file bankStatementID]];

Output:

var statementID: String = String(format: "%05li", CUnsignedLong(file.bankStatementID()))