Formatting Numbers in Swift

Question

I have a formatter

let formatter: NumberFormatter = {
            let formatter = NumberFormatter()
            formatter.numberStyle = .decimal
            formatter.maximumFractionDigits = 8
            return formatter
        }()

I want to let formatter to receive fractions like 1/3, 1/10, 5/115 and convert it into decimal number. Is it possible to fix?

I am expecting to get from 2/3 0.66666667 etc.

Please update your question showing what you have tried. Certainly if you pass `1.0/3.0` into the formatter you will get the correct result. — HangarRash, Nov 16 '22 at 19:33
if i pass 1.0/3.0 in my formatter, i am getting a result "1". Cause this formatter can only read the first part of this number. — Ростислав Ляпкин, Nov 16 '22 at 19:36
@РостиславЛяпкин Please, show as a minimal, reproducible example how you are using the formatter. — Sulthan, Nov 16 '22 at 19:37
TextField("\(matrixA[row-1][column-1])", value: $matrixA[row-1][column-1], formatter: formatter).multilineTextAlignment(.center). Thats an example of using this formatter. User is typing something in TextField. — Ростислав Ляпкин, Nov 16 '22 at 19:39
For example it can be like TextField("\\(a)", value: a, formatter: formatter). a is a Double — Ростислав Ляпкин, Nov 16 '22 at 19:40
Don't post code in comments. Edit your question and add the additional code there (The lack of carriage returns and white space makes anything more than a few characters unreadable in the comments section. Plus future readers shouldn't have to wade through the question and a bunch of comments to understand the question.) — Duncan C, Nov 16 '22 at 19:59

score 1 · Answer 1 · answered Nov 16 '22 at 20:01

1

I don't think NumberFormatters are able to parse mathematical expressions like the string "1.0/3.0".

So I believe the answer to your question is no.

If you do a google search on "swift arithmetic expression parser" it looks like there are few open source frameworks that might do what you want.

answered Nov 16 '22 at 20:01

Duncan C

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That's a bit sad, but thank you for you answer – Ростислав Ляпкин Nov 16 '22 at 20:06
https://stackoverflow.com/a/61114799/2303865 – Leo Dabus Nov 16 '22 at 21:46
That thread shows a `RationalFormatter` that will convert Double values to fractions. The OP needs the opposite: Converting fraction strings to Doubles (which should be easier.) I assume there is a reverse function defined in the Formatter class? (Something like `value(for:String)`.) I’m on an iPad at the moment and don’t have access to the Xcode help system. – Duncan C Nov 17 '22 at 01:59

Formatting Numbers in Swift

1 Answers1