Calculate text height with given width and font

heightOfText.swift

/* Get the height of ONE line text with given width and font */
func heightOfOneLineString(text: String, width: CGFloat, font: UIFont) -> CGFloat {
    let rectOneLine = NSString(string: text).boundingRect(with: CGSize(width: width, height: CGFloat(MAXFLOAT)),
                                                          options: .truncatesLastVisibleLine,
                                                          attributes: [ NSFontAttributeName: font ],
                                                          context: nil)
    return rectOneLine.size.height
}

/* Get the height of MULTIPLE lines text with given width and font */
func heightOfMultipleLinesString(text: String, width: CGFloat, font: UIFont) -> CGFloat {
    let rectMultipleLines = NSString(string: text).boundingRect(with: CGSize(width: width, height: CGFloat(MAXFLOAT)),
                                                                options: .usesLineFragmentOrigin,
                                                                attributes: [ NSFontAttributeName: font ],
                                                                context: nil)
    return rectMultipleLines.size.height
}

http://www.cnblogs.com/willbin/p/3955786.html
http://stackoverflow.com/questions/13621084/boundingrectwithsize-for-nsattributedstring-returning-wrong-size