A nifty extension that I borrowed from DeclarativeHub's ReactiveKit: https://github.com/declarativehub/reactivekit/

NSObject+AnyCancellable.swift

import Combine
import ObjectiveC.runtime

extension NSObject {
    private enum AssociatedKeys {
        static var CancellablesKey = "CancellablesKey"
    }

    /// A set that can be used to dispose of Combine cancellables.
    public var cancellables: Set<AnyCancellable> {
        get {
            if let cancellables = objc_getAssociatedObject(self, &NSObject.AssociatedKeys.CancellablesKey) {
                return cancellables as! Set<AnyCancellable>
            } else {
                let cancellables: Set<AnyCancellable> = []
                objc_setAssociatedObject(self, &NSObject.AssociatedKeys.CancellablesKey, cancellables, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
                return cancellables
            }
        }
        set {
            objc_setAssociatedObject(self, &NSObject.AssociatedKeys.CancellablesKey, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
    }
}