IOS 计算富文本的高度方法

 方式一：

NSMutableAttributedString *attStr = [NSMutableAttributedString new];
CGSize attSize = [attStr boundingRectWithSize:CGSizeMake(UIScreen.mainScreen.bounds.size.width, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading context:nil].size;
CGFloat height = size.height;

NSMutableAttributedString *attStr = [NSMutableAttributedString new];

CGSize attSize = [attStr boundingRectWithSize:CGSizeMake(UIScreen.mainScreen.bounds.size.width, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading context:nil].size;

CGFloat height = size.height;

方式二：

NSMutableAttributedString *attStr = [NSMutableAttributedString new];
CGFloat height = [label sizeThatFits:CGSizeMake(UIScreen.mainScreen.bounds.size.width, CGFLOAT_MAX)].height;

NSMutableAttributedString *attStr = [NSMutableAttributedString new];

CGFloat height = [label sizeThatFits:CGSizeMake(UIScreen.mainScreen.bounds.size.width, CGFLOAT_MAX)].height;