Predefining defensive positions

To defend our tower from the attack of the robots, we will be able to set some defenses, which will be placed in predefined positions, as we want the scenario to look neat.

These positions have been defined in a .plist file that we need to load, so follow these steps:

1. In the project navigator, right-click the Resources group and select Add Files to "DefenseTheTower"….

2. Look for the DefensePositions.plist files in the Resources folder.

3. Be sure that Copy items into destination group's folder (if needed) is selected and click on Add.

In GameScene.m, add the following constant definition:

// Number of defenses
const int kNUM_DEFENSES = 30;

This is the maximum number of defenses and hence the maximum number of predefined positions.

Declare the following array that will contain the list of predefined positions:

 // Declare array of defense positions
 NSMutableArray *_defensePositions;

And call the following method at the end of init just before return self:

 // Load defense...