根据 label 的 text 的大小和长度 获取 尺寸

NSDictionary *attribute = @{NSFontAttributeName: [UIFont systemFontOfSize:17]};
CGSize size = [_cards[1][i] boundingRectWithSize:CGSizeMake(1000, 40) options: NSStringDrawingTruncatesLastVisibleLine | NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading attributes:attribute context:nil].size;
NSLog(@"%f",size.width);