Modify SKActions during the game - ios

Question

I am developing a game where all the enemies are SKNodes in their own classes. Within my SKScene I am spawning the mobs via allocing them and calling a specific method for spawning.
However, when they are spawned each mob are defined with a set of actions they run during their lifetime. One example are for one specific mob is:
SKAction *moveLeft = [SKAction moveToX:0 - (fragment.size.width/2) + (width / 2) duration:1.0];
SKAction *moveRight = [SKAction moveToX:(fragment.size.width / 2) - (width / 2) duration:1.0];
SKAction *sequence = [SKAction sequence:#[moveLeft, moveRight]];
SKAction *bounceOnWalls = [SKAction repeatActionForever:sequence];
[enemy runAction:bounceOnWalls];
So, back to my question. How can I modify a specific SKAction after its been created? I would like to change lets say the speed of moveLeft for all enemies that have this SKAction.

Answer 1

You can run action with key :
SKAction *moveLeft = [SKAction moveToX:0 - (fragment.size.width/2) + (width / 2) duration:1.0];
SKAction *moveRight = [SKAction moveToX:(fragment.size.width / 2) - (width / 2) duration:1.0];
SKAction *sequence = [SKAction sequence:#[moveLeft, moveRight]];
SKAction *bounceOnWalls = [SKAction repeatActionForever:sequence];
[enemy runAction:bounceOnWalls withKey:#"moving"]; //Run action with key
And when you need to change the speed on all nodes which running that action, you can use enumerateChildNodesWithName method. Like this:
[parentNode enumerateChildNodesWithName:name usingBlock:^(SKNode *node, BOOL *stop){
if([node actionForKey:#"moving"]){
SKAction* action = [node actionForKey:#"moving"];
action.speed = 1.5f;
}
}];
You could probably change dynamically duration of actions and affect in that way on speed of moving nodes, but I think that changing speed of an action directly is better choice. Take a look at both answers in this example on how you can change duration parameter dynamically.