func getLongestStringFromArray(strArray:NSArray)->String
{
    var String = ""
    for(var j=0;j<strArray.count;j += 1)
    {
        if(strArraY[j].length > String.length)
        {
            String = strArraY[j] as! String
        }
    }
    return String
}

字符串部分加粗显示

func changePartOfStringToBold(allString:string,boldString:string,fontSize:CGFloat)->NSMutableAttributedString
{
    let attriStr:NSMutableAttributedString = NSMutableAttributedString(String:allString)
    let boldRange = NsmakeRange(NSString(String: allString).rangeOfString(boldString).LOCATIOn,NSString(String: allString).rangeOfString(boldString).length)
    attriStr.addAttribute(NSFontAttributename,value: UIFont(name: "Helvetica-Bold",size: fontSizE)!,range: boldRangE)
    return attriStr
}

字符串部分字符显示不同颜色

func changePartOfStringStyle(allString:string,rangeString:string,isBold:Bool,fontSize:CGFloat)->NSMutableAttributedString
{
    let attriStr:NSMutableAttributedString = NSMutableAttributedString(String:allString)
    let range = NsmakeRange(NSString(String: allString).rangeOfString(rangeString).LOCATIOn,NSString(String: allString).rangeOfString(rangeString).length)
    attriStr.addAttribute(NSForegroundColorAttributename,value: UIColor.redColor(),range: (range ))
    if(isBold == truE)
    {
        attriStr.addAttribute(NSFontAttributename,range: rangE)
    }
    return attriStr
}

取字符串某一个字符后的部分（如：小数点后的字符）

let str = "13.123"
let strArray = str.componentsSeparatedByString(".")
let str2 = ArraY[1]

查找指定字符位置，及获得指定范围的子字符串

let source = "abcdefg"
let str = "c"
let range = NsmakeRange(2,1)


let subRange = (source as NSString).rangeOfString(str)   //子范围
let subString = (source as NSString).subStringWithRange(rangE)  //子字符串