Double

String

import Foundation

extension String {
    /*
     *去掉首尾空格
     */
    var removeHeadAndTailSpace:String {
        let whitespace = NSCharacterSet.whitespaces
        return self.trimmingCharacters(in: whitespace)
    }
    /*
     *去掉首尾空格 包括后面的换行 \\n
     */
    var removeHeadAndTailSpacePro:String {
        let whitespace = NSCharacterSet.whitespacesAndNewlines
        return self.trimmingCharacters(in: whitespace)
    }
    /*
     *去掉所有空格
     */
    var removeAllSapce: String {
        return self.replacingOccurrences(of: " ", with: "", options: .literal, range: nil)
    }
    /*
     *去掉首尾空格 后 指定开头空格数
     */
    func beginSpaceNum(num: Int) -> String {
        var beginSpace = ""
        for _ in 0..<num {
            beginSpace += " "
        }
        return beginSpace + self.removeHeadAndTailSpacePro
    }
}

类型转换

Double <-> String

//String -> Double
let number:Double = Double(numberStr)

//Double -> String
let numberStr = "\(number)"
let numberStr = String(format:"%.2f",number)	//设置保留小数