func greet(person: [String: String]) {
	guard let name = person["name"] else {
		return
	}

	print ("Hello \(name)!")

	guard let location = person["location"] else {
		print("I hope the weather is nice near you.")
		return
	}

	print("I hope the weather is nice in \(location).")
}

greet(person: ["name": "John"])
// 출력
// Hello John!
// 두 번째 guard문은 location 값이 없어 조건이 false가 되고 따라서 else절이 실행된다.
// I hope the weather is nice near you.

greet(person: ["name": "John", "location": "Cupertino"])
// 출력
// Hello John!
// I hope the weather is nice in Cupertino