swift 取出中间文本

func  stringmid (wholestring:String,front:String,behind:String)->String

{

if wholestring.isEmpty

{

return("") //wholestring 不能为nil

}else  {

var whole:NSString=wholestring

let frontindex = whole.rangeOfString(front)

if frontindex.length > 0

{

whole = whole.substringFromIndex(frontindex.location + frontindex.length)

let behindindex = whole.rangeOfString(behind)

if behindindex.length > 0

{

whole = whole.substringToIndex(behindindex.location)

return(whole as String)

} else {return("")} //没有找到behind在wholestring

} else  {return("")}  // 没有找到front 在wholestring

}

}