How do you create random nodes to appear at random times but they do not overlap current nodes in scene? - sprite-kit

Question

I am fairly new to iOS Swift and sprite kit, but I am currently developing a game where I would like items (SKSpriteNodes) to appear at random times and when they do appear, they don't overlap with existing nodes in the game scene.
Below is my code so far for producing a random node and a specified with range time interval to appear across the scene width/height. However, I haven't incorporated the code that allows them to not overlap or be on top of other present nodes in the scene.
override func didMove(to view: SKView) {
let wait = SKAction.wait(forDuration: 10, withRange: 5)
let spawn = SKAction.run {
self.randomFood()
}
let spawning = SKAction.sequence([wait,spawn])
self.run(SKAction.repeat((spawning), count: 5))
}
func randomFood() {
//supposed to pick random point within the screen width
let xPos = randomBetweenNumbers(firstNum: 0, secondNum: frame.width )
let foodNode = SKSpriteNode(imageNamed: "burgerFood") //create a new food item each time
foodNode.position = CGPoint(x: xPos, y: self.frame.size.height/2)
foodNode.setScale(0.10)
foodNode.physicsBody = SKPhysicsBody(circleOfRadius: foodNode.size.width/2)
foodNode.zPosition = 10
foodNode.alpha = 1
foodNode.physicsBody?.affectedByGravity = false
foodNode.physicsBody?.categoryBitMask = 0
foodNode.physicsBody?.contactTestBitMask = 0
addChild(foodNode)
}
func randomBetweenNumbers(firstNum: CGFloat, secondNum: CGFloat) -> CGFloat {
return CGFloat(arc4random()) / CGFloat(UINT32_MAX) * abs(firstNum - secondNum) + min(firstNum, secondNum)
}