Avoiding leaks with __weak - memory-leaks

Question

In sprite kit, I've been trying to work out why my SKScene won't deallocate and I believe I have finally taken a step closer to the answer: I use a lot of SKActions with completion blocks. I have just learned that I must use weak references.
How do I properly do this? Does everything inside the block have to be weak? For example, I just recently changed one of my blocks to look like this:
__weak typeof(self.heli) weakheli = self.heli;
[weakheli runAction:[SKAction fadeAlphaTo:1.0f duration:1.0f] completion:^{
ghostMode = NO;
}];
Do I also have to make a __weak typeof(ghoseMode) weakGhostMode = ghostMode statement and only change weakGhostMode inside the block?
As another example, should:
[weakSelf runAction:[SKAction waitForDuration:.1f] completion:^{
if (mgFiring) {
[self fireMG];
}
}];
Be changed to:
[weakSelf runAction:[SKAction waitForDuration:.1f] completion:^{
if (mgFiring) {
[weakSelf fireMG];
}
}];
Thanks for the help! When I was learning Sprite Kit through tutorials, we were never warned about using completion blocks with strong references.

Answer 1

This does not require __weak because the heli object is used to run the action, it is not referenced inside the block.
__weak typeof(self.heli) weakheli = self.heli;
[weakheli runAction:[SKAction fadeAlphaTo:1.0f duration:1.0f] completion:^{
ghostMode = NO;
}];
So this will be fine:
[self.heli runAction:[SKAction fadeAlphaTo:1.0f duration:1.0f] completion:^{
ghostMode = NO;
}];
Same goes for this:
[weakSelf runAction:[SKAction waitForDuration:.1f] completion:^{
if (mgFiring) {
[weakSelf fireMG];
}
}];
It should be:
[self runAction:[SKAction waitForDuration:.1f] completion:^{
if (mgFiring) {
[weakSelf fireMG];
}
}];
The weakSelf is only needed (if at all) inside the block.