import Cocoa

/* Create a simple closure */
let sayHello = {
    print("Hello, World!")
}

/* Call the closure */
sayHello()

/* Create a function that can take a closure as a parameter */
func sayHelloTo(name: String, withGreeting greeting: () -> ()) {
    print("Hello, \(name)!")
    greeting()
}

/* Call the function, passing in the closure */
sayHelloTo(name: "John", withGreeting: sayHello)

Output

Hello, World!

Hello, John!

Hello, World!