Is there some way in Swift that I can tell when an SKSpriteNode has actually been removed from the scene? I don't think it's actually done when removeFromParent is called, but instead I think it's done later, when Sprite-Kit thinks it's convenient to do so.
I'm trying to understand the full life cycle and I've noticed that a sprite can still be involved in contact and collisions in didBeginContact even after that sprite has been removed.
If I print out the contents of children (i.e. the array holding all the children of the scene) I see that the sprite is removed as soon as removeFromParent called, but the sprite is still available (at least, for this execution of the SK game loop).
Edit: This question came out from an earlier question of mine concerning didBeginContact being called multiple times for one contact (Sprite-Kit registering multiple collisions for single contact) and discovering that removing the sprite during the first contact did not prevent the subsequent contact(s). (Because SK has 'queued' to contacts in advance.) so I was wondering when the sprite is actually removed.
Am I missing the obvious? So even after removeFromParent the sprite is still around. However, it might well be because I have assigned the node to a temporary SKSpriteNode variable, then as long as that variable is around, there is a strong reference to the node, so it won't be deallocated. Also the SKPhysicsContact object itself will retain a reference to the physicsBody, which has a reference to the node which I think will also prevent allocation.
Update
To see when a sprite is actually released, use the deinit() method:
deinit {
print("Invader of type \(type) deinitialised")
}
I think this can only be added in a subclass definition, not via an extension.
Having a variable with a strong reference to the node being removed will prevent the node from being de-allocated until that variable is itself removed or changed to refer to something else.
If I've understand your question, I think it's not needed because you can always do:
if let myNode = self.childNode(withName: "//myNode") {
// ok myNode exist
}
Hope it helps you, you can write this code wherever you think is necessary.
Update:
About the reformulation of your question take a look below to these comments.
I have a suggestion after reading through the comments... move the node to a place outside of the playable area of your game, then remove it from parent. At this point you don't have to worry about when the physics body gets removed or when SK handles it. Or you could set the physicsBody? to nil at the same time, or use a bitmask flag as KoD suggested.
You can override all of the functions in the SK loop and check to see exactly when your pb is removed: https://developer.apple.com/library/content/documentation/GraphicsAnimation/Conceptual/SpriteKit_PG/Actions/Actions.html
Related
This is sort of a stupid question, but what does the function self.addChild() do?
I am familiar with this function, and how to use it, but I am not exactly sure what it adds the child to.
For instance, I have created and designed an SKShapeNode called spinnyNode. Then I call the function:
func touchDown(atPoint pos : CGPoint) {
if let n = self.spinnyNode?.copy() as! SKShapeNode? {
n.position = pos
n.strokeColor = SKColor.black
self.addChild(n)
}
What is the parent in this situation? Is it the view that the node is being created in?
Thank you so much for your time, and your answering of stupid questions.
Lets break it down:
self in this case, refers to the SKScene which your are currently in. So if you're in your gameScene, the node will be added to the gameScene. Note that you can add nodes to other nodes, so if you have an SKNode named gameLayer, you could add a node to gameLayer, which would then be added to the scene. (That would look like this: gameLayer.addChild(node)) If there is no specified location for the node, it default chooses self
addChild(node) is the function that actually adds the specified node to the specified location (see above). You tell the compiler which node to add to the scene by putting its declared name in the brackets.
Make sure you're setting the nodes attributes (position, size, etc...), as they stay the default values until you change them.
The parent is essentially the scene, and what you are doing is adding that node to the scene. Without this call, the node would be created, but never passed to the scene, so it wouldn't spawn.
Think of it as doing some homework for a teacher, then the addChild submits it. If you don't submit it, it isn't used. So whatever class your function is in, be it SKScene etc, that is the parent the node is being passed to.
And don't worry, it isn't a stupid question, learning the foundations of how these functions work is a great way to build better apps!
I've been working on a IOS mobile game and I wanted to take an object,duplicate it, and have the copies move all over the screen. I've looked through Google to find things relevant to this but they were all in Objective C or just didn't have what I was looking for. I want to know how to do this in Swift and SpriteKit.
If you are working with SKSpriteNode you can copy it and all it's current properties with:
let copiedNode = nodeToCopy.copy() as! SKSpriteNode
You will still need need to add copiedNode to your scene. copiedNode will also continue to run any actions that nodeToCopy was running. You can cancel them with copiedNode.removeAllActions().
Note that the documentation for the protocol NSCopying reads exactly:
Protocol
NSCopying
A protocol that objects adopt to provide functional
copies of themselves.
The exact meaning of “copy” can vary from class to class, but a copy
must be a functionally independent object with values identical to the
original at the time the copy was made...
Indeed, in the case of SKSpriteNode, Apple have interpreted that idea so that the copy() function "spawns" another instance of the item, exactly as in any game engine.
(So, for SKSpriteNode copy() works identically to the sense of Instantiate in Unity, say.)
As mogelbuster points out below, there is nowhere in the Apple documentation that they state "The spawn command in Apple is copy()" but in fact they have interpreted this "The exact meaning of “copy” can vary from class to class" in exactly that way for SKNode, since indeed it's a game engine and it's the only meaningful sense of copy there.
It's worth noting that the most completely typical way to work in games is: for your say rocketShips, you would have one "model" of your rocketShip, say modelRocketShip. The model simply sits offscreen, or is perhaps marked as invisible or inactive. You never use the model in the game, it just sits there. When you spawn rocketShips, you just dupe the model. (So in Apple that's modelRocketShip.copy() and then set the position etc.)
You can define a function to create and return a sprite :
func createSprite()->SKSpriteNode{
let sprite = SKSpriteNode(...)//Use the init function in the SKSpriteNode class
//Add some code to define the sprite's property
return sprite
}
And call this function to get some sprites that have the same property:
let spriteOne = createSprite()
let spriteTwo = createSprite()
Then you can add different SKActions to each of them so that they can behave differently.
Once you have multiple SKSpriteNodes, you can also control them by using EnumerateChildNodesWithName (assuming all your nodes have the same name) to go through all of them do do what you want in the update() function.
On a more advanced level, you could subclass SKSpriteNode and incorporate your own behaviour in your custom class.
I have been programming a Break Out app for my swift class and I have been able to figure out everything except for how to remove one of the top paddles from the collision behavior. If someone could tell me how to remove something from the collisionBehavior's array of items, that would be great. Thank you.
Set the dynamic flag to false?
The default value is YES. If the value is NO, the physics body ignores all forces and impulses applied to it. This property is ignored on edge-based bodies; they are automatically static.
SKPhysicsBody Class Reference
I have a scene called Level1, which takes the hero and the enemy from a layer called GameLayer. I heard that an efficient way of doing this is using tags and retrieving it using getChildByTag. I tried this out, but I'm having many issues. I'm using SneakyInput. On Level1, there is a leftJoystick (for enemy movement), and a rightJoystick (for firing projectiles). I have an addEnemy and addHero method in my GameLayer, which I call. Everything I've mentioned works.
In my Level1 scene I have a method called moveHero (which obviously is supposed to move the hero with the joystick.). Through basic debugging I know the problem is the geteChildByTag line. I test out the hero's position through NSLog, and it's saying 0,0. Which is weird because on screen you can see the hero. But I also realized I'm calling the addHero method without using getChildByTag.
I hope I'm being clear here. I've uploaded GameLayer.h and GameLayer.m onto 4shared. http://www.4shared.com/file/PqhjoMFy/GameLayer.html
Hopefully you can take a look at it and point me in the right direction.
BTW: There are no errors or crashes. It's just not working.
Thanks in advance.
getChildByTag will never crash, it's a pretty nicely coded method that just loops through the children array of the object and checks to see if any objects match, that way you don't get assertion issues.
You have some serious issues here with your code.
Firstly..
GameLayer *heroInstance = [[GameLayer alloc] init];
CCSprite *hero = (CCSprite *)[heroInstance getChildByTag:1];
NSLog(#"Hero position X: %f", hero.position.x);
NSLog(#"Hero position Y: %f", hero.position.y);
This will never work, heroInstance is a brand new object, it has no children, also you've just created a memory leak here.
Your hero is a child of the spritesheet, which is a child of the scene.
To reference your child you must call getChildByTag on your spritesheet (which you probably need to reference by calling getChildByTag on your scene..
something like this.
[[self getChildByTag:spritesheet] getChildByTag:hero];
Also, use an enum, so that you don't have to remember what numbers certain tags are (look at the cocos2d example projects).
I am working on a game. There are balls that fall from the top of the screen, and the player has to catch them, as the are caught they stack ontop of one another. I have a method that creates each new ball and adds it to an Array that i use to move the sprites. Problem is that the after they collide I need them to stop moving, since the array is called on to move them they all move. And if i try to make them stop they all stop. So I was hoping to create a pointer attribute if ther is such a think, for example "sprite.position" I need a new attribute that i can check like a boolean. I was hoping to create a attribute like sprite.hasCollided and if it returns YES then the ball should no longer move. Is this possible or is there a better way to do it?
Thanks
Tanner
I would suggest you create a ball object. And add the boolean as as part of the object.
CCNodes (and, by inheritence, CCSprites) have a userData property, which is a void*. You can use this to relate a custom object to a cocos2d object. Keep in mind if you use the userData option, you will, in most cases, need to allocate any memory when you create/assign the sprite, and release it when you are done.
int* myInt = (int*)malloc(sizeof(int));
*myInt = 0;
sprite.userData = myInt;
//some time later, when you are done with the sprite
free(sprite.userData);
As an improvement on the userData property, you can do what xuanweng suggests and create a ball object containing various game-related properties for the balls, and assign an instance of this to each of your ball CCSprites using the method above.