Memory Leak Test

I have a class named PERSON to test memory leak. Here are the contents of class:

let name: String
private var actionClosure: (() -> ())!

init (name: String) {
    self.name = name
    self.actionClosure = {
        println("I am (self.name)")
    }
}

func performAction () {
    actionClosure()
}

deinit {
    println("(name) is being deinitialized")
}

Anyway, the book I am following wrote a code inside ViewController.swift. Beneath the viewDidLoad() method. Here are contents:

let person = Person(name: "randomName"); person.performAction();

The part I didn't understand is this: We initialize something with String. I get it but how does the class directly becomes able to use this? Like how does it know to take that init? I really didn't understand what happened there. It would be awesome if someone can explain the class and what happened in it.