[iOS]iOS7で文字列のサイズを求める

//iOS6まで、非推奨
CGSize size = [textLabel.text sizeWithFont:[UIFont systemFontOfSize:fontSize]
                         constrainedToSize:textLabel.size
                             lineBreakMode:UILineBreakModeWordWrap];
//iOS7
CGSize size = [textLabel.text boundingRectWithSize:textLabel.size
                                           options:NSStringDrawingTruncatesLastVisibleLine|NSStringDrawingUsesLineFragmentOrigin
                                        attributes:@{NSFontAttributeName:textLabel.font} context:nil].size;