How can I make the player not able to go through certain boundaries? (off-screen) - swift

Question

Hey so I was watching Ray Wenderlich's tutorial on How to Make a Game Like Mega Jump! and tried to create a similar project on my own. So during the tutorial you set the player to be able to go off the screen whenever you tilt the device.
override func didSimulatePhysics() {
player.physicsBody?.velocity = CGVector(dx: xAcceleration * 400.0, dy: player.physicsBody!.velocity.dy)
if player.position.x < -20.0 {
player.position = CGPoint(x: self.size.width + 20.0, y: player.position.y)
} else if (player.position.x > self.size.width + 20.0) {
player.position = CGPoint(x: -20.0, y: player.position.y)
}
return;
}
This is the code I have which makes the player go off the screen. How can I do this but for the player NOT being able to go off the screen? For example if you tilt your device all the way to the right make the player to stay on the right side until you move it the other way! Thank you in advance.

Answer 1

Currently you check if the player is out of screen (more then 20px) and then set his position to the other side, 20px out of the screen.
But you want to stop the player at 0px and your screen width. You can do it like this:
if player.position.x <= 0.0 {
player.position = CGPoint(x: 0.0, y: player.position.y)
} else if (player.position.x >= self.size.width) {
player.position = CGPoint(x: self.size.width, y: player.position.y)
}
This just set's the position of the player to 0.0 if he's moving out to the left, or your screen width, if he's moving out to the right.

Answer 2

The current code "loops around" so moving all the way to the left means you end up on the right.
Just change the coordinates in the if blocks to pin to the edges. Something like this:
if player.position.x < -20.0 {
player.position = CGPoint(x: -20.0, y: player.position.y)
} else if (player.position.x > self.size.width + 20.0) {
player.position = CGPoint(x: self.size.width + 20.0, y: player.position.y)
}
Notice that if the player is beyond the left edge (x < -20) then you just leave the x-position at -20. Similar thing on the right edge.
You'll have to try this out to see how it works with the physics and acceleration but that should be the general idea.