Generate random values based on a seed Swift 3 - swift

Question

lets say you were making a game and this game has procedurally generated terrain from a seed that the user inputted in his world-creation menu
and this seed generates a set of values that only change if the seed changes
for instance lets say you want to get a random set of integers to generate in a for-loop and pull randomly from an array the set of integers stay the same every time and pull the same items from the array in the exact same order every time you run the for-loop until you change the seed
how would one achieve this in swift
in my code here i can get the terrain to spawn in but it does not generate the same every time which is what i am trying to get it to do
override func didMove(to view: SKView) {
let tile1 = SKTileDefinition(texture: SKTexture(imageNamed: "stone") ,size: CGSize(width: 64, height: 64))
let tile2 = SKTileDefinition(texture: SKTexture(imageNamed: "water") ,size: CGSize(width: 64, height: 64))
let tile3 = SKTileDefinition(texture: SKTexture(imageNamed: "sand") ,size: CGSize(width: 64, height: 64))
let tile4 = SKTileDefinition(texture: SKTexture(imageNamed: "grass") ,size: CGSize(width: 64, height: 64))
let tileGroup1 = SKTileGroup(tileDefinition: tile1)
let tileGroup2 = SKTileGroup(tileDefinition: tile2)
let tileGroup3 = SKTileGroup(tileDefinition: tile3)
let tileGroup4 = SKTileGroup(tileDefinition: tile4)
let tileGroup5 = SKTileGroup(tileDefinition: tile4)
let tileGroup6 = SKTileGroup(tileDefinition: tile4)
let tileSet = SKTileSet(tileGroups: [tileGroup1,tileGroup2,tileGroup3,tileGroup4,tileGroup5,tileGroup6])
let columns = 5
let rows = 5
let tileSize = CGSize(width: 64, height: 64)
//this is another GKNoise class called Noise
let noise = Noise()
let noiseMap = GKNoiseMap(noise, size: vector_double2(10.0,10.0), origin: vector_double2(0.0,0.0), sampleCount: vector_int2(100), seamless: true)
//this is another SKTileMapNode Class called TileMap and a class func called tileMapNodes
let tileMap = TileMap.tileMapNodes(tileSet: tileSet, columns: columns, rows: rows, tileSize: tileSize, from: noiseMap, tileTypeNoiseMapThresholds: [(-1.0 as NSNumber),(+1.0 as NSNumber)])
tileMapNode = tileMap.first!
let seed = Int
for column in 0 ..< tileMapNode.numberOfColumns {
for row in 0 ..< tileMapNode.numberOfRows {
let rand = Int(arc4random_uniform(UInt32(tileSet.tileGroups.count)))
print(rand)
let tile = tileMapNode.tileSet.tileGroups[rand]
tileMapNode.setTileGroup(tile, forColumn: column, row: row)
}
}

Answer 1

If you want to generate a random value based on a specific seed use: srand48 and drand48:
srand allow you to specify the seed:
srand48(230)
Then drand48 will give you a double between 0 and 1:
let doubleValue = drand48()
So in your case, if you want an Int between 0 and 9, you can do something like:
srand48(230)
print("Random number: \(1 + Int((drand48() * 8) + 0.5))")
print("Random number: \(1 + Int((drand48() * 8) + 0.5))")
print("Random number: \(1 + Int((drand48() * 8) + 0.5))")
It will give you the 3 pseudo random numbers until you change the seed
Here is the drand48 applied to your new question:
let seed = srand48(230)
for column in 0 ..< tileMapNode.numberOfColumns {
for row in 0 ..< tileMapNode.numberOfRows {
let rand = Int(Double(tileSet.tileGroups.count) * drand48() - 0.5)
print(rand)
let tile = tileMapNode.tileSet.tileGroups[rand]
tileMapNode.setTileGroup(tile, forColumn: column, row: row)
}
}