How to programmatically sizeToFit width AND height on UILabel?

I'm programmatically creating multi-line UILabels ([label setNumberOfLines:0];).

The built-in sizeToFit method of UILabel works great for 1 line UILabels, but for multi-line text, it sets the height properly, but the width is set too small, causing longer text lines to wrap.

I don't know the label width until after the user enters their text. I want to resize the labels to fit the width of the longest line of text. And per @DonMag's comment, I also want to restrict the label to not be wider than the screen.

I tried different lineBreakMode settings but there isn't a 'nowrap' option.

I've searched SO and there are many related solutions but none that solve the problem of sizeToFit for both width and height.

Is there a way to programmatically size a multi-line UILabel to fit BOTH the width AND the height of the text?

Solution

You can do this with boundingRectWithSize...

Add your label to the view and give it a starting width constraint (doesn't really matter what value, as it will be changed).

Keep a reference to that width constraint (IBOutlet works fine if you're using IB).

Don't give it a height constraint.

When you set the text of the label, you can use this to change its width:

// get the font of the label
UIFont *theFont = _theLabel.font;

// get the text of the label
NSString *theString = _theLabel.text;

// calculate the bounding rect, limiting the width to the width of the view
CGRect r = [theString boundingRectWithSize:CGSizeMake(self.view.frame.size.width, CGFLOAT_MAX)
                                   options:(NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading)
                                attributes:@{NSFontAttributeName: theFont}
                                   context:nil];

// change the constant of the constraint to the calculated width
_theWidthConstraint.constant = ceil(r.size.width);

// NOTE: If you are *not* using auto-layout, 
// this same calculation can be used to explicitly set
// the .frame of the label.

Edit:

As per the OP's requirement, a complete, runnable example -- using code only, no storyboards / IB -- can be found here: https://github.com/DonMag/MultilineLabelFitWidth

Edit 2:

GitHub project updated... now includes examples for both manual frame setting and auto layout / constraints.