Timelines & Triggers - Learn SpriteBuilder for iOS Game Development - page 154

@implementation Trigger
{
BOOL _repeatsForever;
}
-(void) didLoadFromCCB
{
if (targetArrays == nil)
{
targetArrays = [NSMutableDictionary dictionary];
triggerArrays = [NSMutableDictionary dictionary];
}
[targetArrays removeAllObjects];
[triggerArrays removeAllObjects];
_repeatsForever = (_triggerCount <= 0);
}
@end
At first, two static NSMutableDictionary variables are declared. The keyword
static means these variables will be shared with all instances of the Trigger class.
Essentially, they are global variables, but because they are declared in the scope of the im-
plementation file they are accessible only to code in the Trigger.m file.
The @implementation section declares an ivar _repeatsForever , which will be
used to determine whether this particular trigger instance will never remove itself.
The didLoadFromCCB method contains initialization and cleanup code for the two
global dictionaries. If targetArrays is nil , it will create an NSMutableDiction-
ary instance and assign it. The same is done for triggerArrays because it can
simply be assumed that if targetArrays is nil then triggerArrays will be nil, too.
Next, both dictionaries are instructed to removeAllObjects . That's kind of odd on
first sight, right?
Here's to foresight: eventually you'll be able to change levels. Given that the two diction-
aries are global ( static ) variables, they and their contents will remain in memory as
you switch levels and present other scenes. So in every new level that contains at least one
Trigger instance, those dictionaries need to be cleared of any remaining references.