How to adjust font size of label to fit the rectangle?

Question

Yeah, there\'s this cool myLabel.adjustsFontSizeToFitWidth = YES; property. But as soon as the label has two lines or more, it won\'t resize the text to anythin

Answer 1

Here's a Swift extension for UILabel. It runs a binary search algorithm to resize the font and bounds of the label, and is tested to work for iOS 12.

USAGE: Resizes the font to fit a size of 100x100 (accurate within 1.0 font point) and aligns it to top.

let adjustedSize = .fitFontForSize(CGSizeMake(100, 100))
.frame = CGRect(x: 0, y: 0, width: 100, height: adjustedSize.height)

Copy/Paste the following into your file:

extension UILabel {
    @discardableResult func fitFontForSize(_ constrainedSize: CGSize,
                                           maxFontSize: CGFloat = 100,
                                           minFontSize: CGFloat = 5,
                                           accuracy: CGFloat = 1) -> CGSize {
        assert(maxFontSize > minFontSize)

        var minFontSize = minFontSize
        var maxFontSize = maxFontSize
        var fittingSize = constrainedSize

        while maxFontSize - minFontSize > accuracy {
            let midFontSize: CGFloat = ((minFontSize + maxFontSize) / 2)
            font = font.withSize(midFontSize)
            fittingSize = sizeThatFits(constrainedSize)
            if fittingSize.height <= constrainedSize.height
                && fittingSize.width <= constrainedSize.width {
                minFontSize = midFontSize
            } else {
                maxFontSize = midFontSize
            }
        }

        return fittingSize
    }
} 

This function will not change the label size, only the font property is affected. You can use the returned size value to adjust the layout of the label.