Sample Game: Side-Scroller for iOS - Game Programming Algorithms and Techniques - page 323

If you browse all the folders in the project, you might see a huge number of files,
most of which are in the libs directory. But all of these source files are the base
cocos2d files; they are not files that were created specifically for Ship Attack .
Therefore, don't bother looking through those source files. You are only interested
in the handful of files that are in the main shipattack directory.
AppDelegate
The AppDelegate class contains didFinishLaunchingWithOptions ,
which is the (rather verbose) entry point ofany iOS program. Forthe purposes ofa
cocos2d game, almost all of the code related to the AppDelegate is auto-gener-
ated. The AppDelegate created by the template normally launches into a scene
called HelloWorld . For this game, I've modified it so that the first scene it goes
into is instead the main menu.
The only other change made to the auto-generated AppDelegate code was to
enable multitouch, which is what allows the game to respond to multiple finger
presses. Without multitouch, the control scheme for this game would not function
properly, because one finger controls movement and the other controls firing.
MainMenuLayer
MainMenuLayer has a class method called scene that returns a CCScene that
contains MainMenuLayer as its only CCLayer . This is the recommended ap-
proach in cocos2d when a scene has only one layer. The layer itself has very little
code in it. All it does is show the title of the game and creates a menu with one
option (to start the game). Menus can be set up in cocos2d using CCMenu and
CCMenuItem , and a particular menu item can have a segment of code that is ex-
ecuted when the item is selected. In this case, when the Start Game option is se-
lected, the game transitions into the GameplayScene .
GameplayScene
As you might expect, the GameplayScene is the scene representing the main
gameplay. If you look at this file, you'll see that there are three different layers:
two ScrollingLayers and the ObjectLayer . The two ScrollingLay-
ers are used for the nebula and star field, whereas the ObjectLayer is where
all the objects in the world (as well as the score display) reside.
GameplayScene really does not do much else other than have an update func-
tion that gets called every frame. This function, in turn, updates the layers. Finally,