根据字符串长度来计算高度

废话不讲了， 直接上代码吧！！！！

+ (CGFloat)heightFromViewWithFont:(UIFont *)font andWidth:(CGFloat)width textContent:(NSString *)textStr

{

    CGSize textBlockSize = CGSizeMake(width, CGFLOAT_MAX);

    CGSize retSize;

    retSize = [textStr boundingRectWithSize:textBlockSize options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading attributes:@{NSFontAttributeName:font} context:nil].size;

    return retSize.height;

}