Custom Font Sizing in Xcode 6 Size Classes not working properly with Custom Fonts

Fast fix:

1) Set fonts as System for size classes

2) Subclass UILabel and override "layoutSubviews" method like:

- (void)layoutSubviews{  [super layoutSubviews];   // Implement font logic depending on screen size    if ([self.font.fontName rangeOfString:@"bold" options:NSCaseInsensitiveSearch].location == NSNotFound) {        NSLog(@"font is not bold");        self.font = [UIFont fontWithName:@"Custom regular Font" size:self.font.pointSize];    } else {        NSLog(@"font is bold");        self.font = [UIFont fontWithName:@"Custom bold Font" size:self.font.pointSize];    }}

By the way, it is a very convenient technique for iconic fonts

After trying everything, I eventually settled on a combination of the above solutions. Using Xcode 7.2, Swift 2.

import UIKitclass LabelDeviceClass : UILabel {    @IBInspectable var iPhoneSize:CGFloat = 0 {        didSet {            if isPhone() {                overrideFontSize(iPhoneSize)            }        }    }    @IBInspectable var iPadSize:CGFloat = 0 {        didSet {            if isPad() {                overrideFontSize(iPadSize)            }        }    }    func isPhone() -> Bool {        // return UIDevice.currentDevice().userInterfaceIdiom == .Phone        return !isPad()    }    func isPad() -> Bool {        // return UIDevice.currentDevice().userInterfaceIdiom == .Pad        switch (UIScreen.mainScreen().traitCollection.horizontalSizeClass, UIScreen.mainScreen().traitCollection.verticalSizeClass) {        case (.Regular, .Regular):            return true        default:            return false        }    }    func overrideFontSize(fontSize:CGFloat){        let currentFontName = self.font.fontName        if let calculatedFont = UIFont(name: currentFontName, size: fontSize) {            self.font = calculatedFont        }    }}

• @IBInspectable lets you set the font size in the Storyboard
• It uses a didSet observer, to avoid the pitfalls from layoutSubviews() (infinite loop for dynamic table view row heights) and awakeFromNib() (see @cocoaNoob's comment)
• It uses size classes rather than the device idiom, in hopes of eventually using this with @IBDesignable
• Sadly, @IBDesignable doesn't work with traitCollection according to this other stack article
• The trait collection switch statement is performed on UIScreen.mainScreen() rather than self per this stack article

Workaround for UILabel: keep the same font size on all Size Classes, but instead change your label height accordingly in each Size Class. Your label must have autoshrink enabled. It worked nicely in my case.