var specializationTitles = ["a","b","c","d"]
let outputString = join(" / ",specializationTitles)
发生错误：
Cannot invoke
joinwith an argument list of type(String,[String])
如何解决这个问题？
let separator = " / " let outputString = separator.join(specializationTitles)
与Xcode7beta6：
specializationTitles.joinWithString(" / ")
使用Xcode7发布版本：
specializationTitles.joinWithSeparator(" / ")
