formaterNumber

gistfile1.txt

    static func formaterNumber(_ number: Double) -> String {
        
        if number < 1e4 {
            return "\(number)"
        }
        
        if number >= 1e4 && number < 1e5 {
            return String(format: "%.1f", number / 1e4) + "万"
        }
        
        if number >= 1e5 && number < 1e6 {
            return String(format: "%.1f", number / 1e5) + "十万"
        }
        
        if number >= 1e6 && number < 1e7 {
            return String(format: "%.1f", number / 1e6) + "百万"
        }
        
        if number >= 1e7 && number < 1e8 {
            return String(format: "%.1f", number / 1e7) + "千万"
        }
        
        return String(format: "%.1f", number / 1e8) + "亿"
    }

gistfile2.txt

typealias NumberContext = (unit: Double, descriptor: String)

let numberContexts: [NumberContext] = {
      [
         NumberContext(1e4, "万"),
         NumberContext(1e5, "十万"),
         NumberContext(1e6, "百万"),
         NumberContext(1e7, "千万"),
         NumberContext(1e8, "亿"),
         NumberContext(1e9, "十亿"),
     ]
 }()
 
 let numberFormatter: NumberFormatter = {
     let formatter = NumberFormatter().then {
         $0.maximumFractionDigits = 1
     }

     return formatter
 }()
 
 func formatNumber(_ number: Double, descriptor: String = "") -> String {
        guard let pureString = numberFormatter.string(from: NSNumber(value: number)) else {
            return "\(number)" + descriptor
        }
        return pureString + descriptor
 }
 
 func formaterNumber(_ number: Double) -> String {
      var prevContext = numberContexts[0]
        for (index, numberContext) in numberContexts.enumerated() {
            if index == 0 {
                if number < numberContext.unit {
                    return formatNumber(number)
                }
            } else {
                if number >= prevContext.unit && number < numberContext.unit {
                    return formatNumber(number / prevContext.unit, descriptor: prevContext.descriptor)
                }
            }

            prevContext = numberContext
        }

        return formatNumber(number / prevContext.unit, descriptor: prevContext.descriptor)
}