[First Class Functions] From John Sundell (https://www.swiftbysundell.com/articles/first-class-functions-in-swift/)

FirstOrderFunctions.swift

// Introducing a 'combine' function for applying a value to
// any function or closure:
func combine<A, B>(
    _ value: A,
    with closure: @escaping (A) -> B
) -> () -> B {
    return { closure(value) }
}

// Example

// A view controller that currently captures 'self' weakly, in
// order to call a method on a 'productManager' property object:
class ProductViewController: UIViewController {
    ...

    override func viewDidLoad() {
        super.viewDidLoad()

        buyButton.handler = { [weak self] in
            guard let self = self else {
                return
            }

            self.productManager.startCheckout(for: self.product)
        }
    }
}

// Using our new combine function:
class ProductViewController: UIViewController {
    ...

    override func viewDidLoad() {
        super.viewDidLoad()
        
        buyButton.handler = combine(product,
            with: productManager.startCheckout
        )
    }
}