swift5.0上报警告：substring(to:)' is deprecated: Please use String slicing subscript with a 'partial range upto' opera
解决办法：
// 从初始位置到index位置
letsubStr=String(value[..<index]) // = str.substring(to: index) is deprecated
// 从index位置到字符串最后
letsubStr=String(value[index...]) // = str.substring(from: index) is deprecated
// 字符串截取中间一段
letsubStr=String(value[range]) // = str.substring(with: range) is deprecated
