Selecting and Unlocking Levels - Learn SpriteBuilder for iOS Game Development - page 266

So far, the GameScene has relied on the ordering of nodes in SpriteBuilder to determine
the draw order. The level content ( _levelNode ) is drawn first, and then the
GameMenuLayer is drawn on top of the level.
However, now you are removing the _levelNode , loading a new one, and adding it as a
child node to the GameScene . Adding a node will always put it at the end of the list;
therefore, the draw order is now reversed, and you can no longer see the pause button.
To fix this, replace the addChild: line of Listing 8-15 with the one in Listing 8-15 .
Listing 8-15 . Fixing the draw order
level.zOrder = -1;
[self addChild:level];
The zOrder property determines the node's draw order. Nodes with a lower zOrder are
drawn before nodes with a higher zOrder , but only if they have the same parent. Nodes
with the same zOrder are drawn in the order they were added to the parent. Note that the
preceding code can be shortened to a single line:
[self addChild:level z:-1];
Now loading levels works! But you want proof? Okay, there's one thing to consider, any-
way: right now the GameScene references the Level1.ccb in the GameScene.ccb file. So
when you load the GameScene , it will actually load the Level1.ccb along with it, and
then replace it with a newly loaded instance of whatever level you chose to load. That's
kind of inefficient, having two levels loaded one after the other and having both in
memory at the same time.
Adding a Dummy Level
To fix this, go into SpriteBuilder and right-click the Levels folder. Select New File , and
name it DummyLevel.ccb . Set its type to Node , and click Create . That's all. You just need
an empty CCB.
Now open the GameScene.ccb , and select the level Content node. On the Item Properties
tab, click the CCB File drop-down menu. Select the newly created Levels/
DummyLevel.ccb as the Sub File node's reference. The GameScene will be empty now
except for the pause button in the upper left corner.