How to get the ascent and descent of a specific string with font applied

Question

Saved Custom Font data to UIFont.

UIFont* font = [UIFont fontWithName:@"SourceHanSans-Medium" size:nEmSize];

Now I want to get the height of a string.

However, the value of nEmSize, which is the size of the font, is returned for the height of the string.

NSDictionary *userAttributes = @{NSFontAttributeName: font, NSForegroundColorAttributeName: [UIColor blackColor]};
const CGSize textSize = [strText sizeWithAttributes: userAttributes];

return (NSInteger)(floor(textSize.height));

So I thought of doing a descent - ascent on the FontMetrics data.
But I did a search and looked up the documentation, but couldn't find a way to get a value from UIFont.

Is there a way to get the descent value and ascent value of a specific string with font applied?