CustomMeasurementFormatter.swift

import Foundation
import UIKit

extension Double {
    func formatElevation() -> (AttributedString, AttributedString) {
        let measurement = Measurement(value: self, unit: Locale.current.usesMetricSystem ? UnitLength.meters : UnitLength.feet)
        var resultString = measurement.formatted(.measurement(width: .narrow, usage: .road, numberFormatStyle: .number).attributed)
        
        let unitContainer = AttributeContainer.measurement(.unit)
        let colorContainer = AttributeContainer.foregroundColor(.white)
        
        resultString.replaceAttributes(unitContainer, with: colorContainer)
        
        var resultStringCopy = resultString
        
        // The closure will be called multiple times, and $0.value will be nil or not depending on if it's in the color range or not
        resultString.transformingAttributes(AttributeScopes.UIKitAttributes.ForegroundColorAttribute.self) {
            if $0.value == nil {
                resultString.removeSubrange($0.range)
            } else {
                resultStringCopy.removeSubrange($0.range)
            }
            
            
        }
        
        return (resultStringCopy, resultString)
    }
}


print (35.0.formatElevation())

//(40 {
//    Foundation.MeasurementAttribute = value
//    Foundation.NumberFormatPart = integer
//}, m {
//    NSColor = UIExtendedGrayColorSpace 1 1
//})
//