Draw a line between two objects - swift

Question

I try to write simple app to draw vertexes and edges between them. I successfully wrote code to add vertexes, delete them and drag around the view. But when I tried to draw a line between them I came across problems. A lot of guide about this are outdated with old versions of Swift or about IOS development so I didn't find how to implement this.
I tried just to draw a line between to points, but nothing worked, also noticed that I want to change coordinates of edge when I drag the vertex.
import Cocoa
var merging = false
var mergingCoords:[CGPoint] = []
class Vertex {
var number:Int
init(number: Int) {
self.number = number
}
}
class Graph {
var size = 0
}
class VertexView: NSBox {
var point: CGPoint = CGPoint(x: 0, y: 0)
required init(coder decoder: NSCoder) {
super.init(coder: decoder)!
}
override init(frame frameRect: NSRect) {
super.init(frame: frameRect)
}
override func mouseDown(with event: NSEvent) {
if (merging) {
print("Really")
mergingCoords.append(self.point)
if (mergingCoords.count == 2) {
// DRAW AN EDGE
}
} else {
point = event.locationInWindow
}
}
override func mouseUp(with event: NSEvent) {
if (!merging) {
if (event.locationInWindow == point) {
self.removeFromSuperview()
} else {
point = event.locationInWindow
}
}
}
override func mouseDragged(with event: NSEvent) {
if (!merging) {
self.frame = NSRect(x: event.locationInWindow.x - 20, y: event.locationInWindow.y - 20, width: 40, height: 40)
}
}
}
class ViewController: NSViewController {
var graph: Graph = Graph()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func viewDidAppear() {
view.window?.makeFirstResponder(self)
}
override func keyDown(with event: NSEvent) {
print(event.characters!)
if (event.characters! == "M") {
merging = !merging;
mergingCoords.removeAll()
}
print(merging)
}
override var representedObject: Any? {
didSet {
// Update the view, if already loaded.
}
}
override func mouseDown(with event: NSEvent) {
let v = VertexView(frame: NSRect(x: event.locationInWindow.x - 20, y: event.locationInWindow.y - 20, width: 40, height: 40))
v.boxType = NSBox.BoxType.custom
v.point = event.locationInWindow
v.cornerRadius = 20
graph.size = graph.size + 1
self.view.addSubview(v)
}
}