iOS UILabel根據內容動態計算高度

NSString *know = @"xxooxxoo......";

CGSize knowSize = [know sizeWithFont:label.font constrainedToSize:CGSizeMake(label.frame.size.width, 1000) lineBreakMode:label.lineBreakMode];

    CGFloat knowH = MAX(24, knowSize.height)+10;

    label.frame = CGRectMake(10, 0, YDeviceWidth - 20, knowH);