Swift:NSLengthFormatter只有1个小数位数

我使用NSLengthFormatter显示正确的实体,如米,脚,码等.
该方法有效,但我没有得到正确数量的小数位数.

let distance = getDistanceAsDouble() //636.62084358567 in meters
        let format = String(format: "%.1f",distance) //636.6

        if let formattedDouble = Double(format) {
            let lengthFormatter = NSLengthFormatter()
            let formattedDistance = lengthFormatter.stringFromMeters(formattedDouble) 
            lbl.text = "\(formattedDistance)" // printed: 697.936 yd
        }

我用Google搜索,但我找不到如何配置NSLengthFormatter.NSNumberFormatter具有类似numberStyle或的属性maximumFractionDigitis,但NSLengthFormatter没有...或？

我试图施放formattedDistance到Double,我可以String(format: ""...再次使用.这不起作用,因为formattedDistance包含"yd"(或其他实体).

我该如何解决这个问题？

NSLengthFormatter有一个属性numberFormatter: NSNumberFormatter,所以用它来设置它,就像这样......

if let formattedDouble = Double(format) {
    let lengthFormatter = NSLengthFormatter()
    lengthFormatter.numberFormatter.maximumFractionDigits = 1 // *****
    let formattedDistance = lengthFormatter.stringFromMeters(formattedDouble)
    print("\(formattedDistance)") 
}