objective c - iPhone UILabel sizeWithFont:

Question

I'm trying to measure the visual size of a NSString that takes into account the number of lines I can render. However, sizeWithFont doesn't take into account numberOfLines property? So my layout algorithm positions everything lower than they actually need to be.

_price = [[UILabel alloc] init];
_price.text = myPriceValue;
_price.lineBreakMode = UILineBreakModeWordWrap;
_price.numberOfLines = 3;
_price.backgroundColor = [UIColor clearColor];
_price.textColor = TTSTYLEVAR(colorPrice);
/// the follow code ignores numberOfLines and just tells me the size of the whole block.  
// I'd like it to be aware of numberOfLines
//
CGSize priceSize = [_price.text sizeWithFont:_price.font
        constrainedToSize:CGSizeMake(maxWidth, CGFLOAT_MAX)
        lineBreakMode:UILineBreakModeWordWrap];

Does anyone know how to do this using the iPhone SDK?

Answer 1

Instead of CGFLOAT_MAX for the max height of your text calculation, try getting the size of one line with this:

[_price.text sizeWithFont:_price.font].height

and then multiplying that by the maximum # of lines you want, then plugging that into the height of the size you are constraining yourself to. It'd probably look like this:

_price = [[UILabel alloc] init];
_price.text = myPriceValue;
_price.lineBreakMode = UILineBreakModeWordWrap;
_price.numberOfLines = 3;
_price.backgroundColor = [UIColor clearColor];
_price.textColor = TTSTYLEVAR(colorPrice);
CGFloat lineHeight = [_price.text sizeWithFont:_price.font].height;
CGSize priceSize = [_price.text sizeWithFont:_price.font
        constrainedToSize:CGSizeMake(maxWidth, lineHeight * _price.numberOfLines)
        lineBreakMode:UILineBreakModeWordWrap];

Don't use this if you ever set number of lines to 0 as your max height will be 0 in that case; you should use CGFLOAT_MAX then.