DynamicClass.swift

@objc class SuperClassA: NSObject {
    
    public required override init() { }
    
    public static var shared: SuperClassA {
        if let instance = _shared {
            return instance
        }

        return instance
    }

    public static var _shared: SuperClassA?

    private static var instance: SuperClassA {
        if let subClassB = NSClassFromString("ModuleB.SubClassB") as? SuperClassA.Type {
            _shared = subClassB.init()
        } else {
            _shared = SuperClassA()
        }

        return _shared!
    }
    
    func sampleFunction() {
        print("super class from module A")
    }
}

// ModuleB
class SubClassB: SuperClassA {
    required init() { }
    
    override func sampleFunction() {
        print("sub class from module B")
    }
}