Having trouble getting UIView sizeToFit to do anything meaningful

Question

When I add a subview to a UIView, or when I resize an existing subview, I would expect [view sizeToFit] and [view sizeThatFits] to ref

Answer 1

        self.errorMessageLabel.text = someNewMessage;

    // We don't know how long the given error message might be, so let's resize the label + containing view accordingly
    CGFloat heightBeforeResize = self.errorMessageLabel.frame.size.height;

    [self.errorMessageLabel sizeToFit];

    CGFloat differenceInHeightAfterResize = self.errorMessageLabel.frame.size.height - heightBeforeResize;

    self.errorViewHeightContstraint.constant = kErrorViewHeightConstraintConstant + differenceInHeightAfterResize;

This worked for me.