Swift字符串过滤空格和换行符，写法与原来的objective-c有点不同，因为Swift中的字符串的索引不是int类型，而是Index类型。

@H_403_5@/// UIView's useful extensions.
@H_403_5@///
@H_403_5@/// Author: huangyibiao
@H_403_5@/// Github: http://github.com/CoderJackyHuang/
@H_403_5@/// Blog: http://www.hybblog.com/
extension String {  
  @H_403_5@/// Get the length of a string
  public func hyb_length() ->Int {
    return self.characters.count
  }

  @H_403_5@/// 去掉字符串前后的空格，根据参数确定是否过滤换行符
  @H_403_5@///
  @H_403_5@/// - parameter trimNewline 是否过滤换行符，默认为false
  public func hyb_trim(trimNewline: Bool = false) ->String {
    if trimNewline {
      return self.stringByTrimmingCharactersInSet(.whitespaceAndNewlineCharacterSet())
    }

    return self.stringByTrimmingCharactersInSet(.whitespaceCharacterSet())
  }

  @H_403_5@/// 去掉字符串前面的空格，根据参数确定是否过滤换行符
  @H_403_5@///
  @H_403_5@/// - parameter trimNewline 是否过滤换行符，默认为false
  public func hyb_trimLeft(trimNewline: Bool = false) ->String {
    if self.isEmpty {
      return self
    }

    var index = self.startIndex
    while index != self.endIndex {
      let ch = self.characters[index]
      if ch == Character(" ") {
        index++
        continue
      } else if ch == Character("\n") {
        if trimNewline {
          index++
          continue
        } else {
          break
        }
      }

      break
    }

    return self.substringFromIndex(index)
  }

  @H_403_5@/// 去掉字符串后面的空格，根据参数确定是否过滤换行符
  @H_403_5@///
  @H_403_5@/// - parameter trimNewline 是否过滤换行符，默认为false
  public func hyb_trimRight(trimNewline: Bool = false) ->String {
    if self.isEmpty {
      return self
    }

    var index = self.endIndex.predecessor()
    while index != self.startIndex {
      let ch = self.characters[index]
      if ch == Character(" ") {
        index--
        continue
      } else if ch == Character("\n") {
        if trimNewline {
          index--
          continue
        } else {
          index++
          break
        }
      }

      break
    }

    return self.substringToIndex(index)
  }
}

转自： Swift trim space/new line