动态计算文字的高度

+ (CGSize)sizeWithText:(NSString *)text andFont:(UIFont *)font andMaxSize:(CGSize)maxSize
{
    CGSize expectedLabelSize = CGSizeZero;
    
    NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
    paragraphStyle.lineBreakMode = NSLineBreakByWordWrapping;
    [paragraphStyle setLineSpacing:0];
    NSDictionary *attributes = @{NSFontAttributeName:font, NSParagraphStyleAttributeName:paragraphStyle.copy};
    
    expectedLabelSize = [text boundingRectWithSize:maxSize options:NSStringDrawingUsesLineFragmentOrigin attributes:attributes context:nil].size;
    
    return CGSizeMake(ceil(expectedLabelSize.width), ceil(expectedLabelSize.height));
}