Error is straight forward and its because of wrong placeholders you have used in function call. Inside init
you are not passing any parameters to your function. It should be this way
destination = Node("some key", neighbors: [edge1 , edge2], visited: true, lat: 23.45, long: 45.67) // fill up with your dummy values
Or you can just initialise with default method
destination = Node()
UPDATE
Add empty initialiser in your Node class
init() {
}