Timelines & Triggers - Learn SpriteBuilder for iOS Game Development - page 165

Since playing an animation when activated by a trigger will be a common use case, it
makes sense to write a generic class PlayTimelineWhenTriggered . But before you
write this class, open Saw1_noautoplay.ccb in SpriteBuilder, and then select the
root node. Do not select the saw sprite. Switch to the Item Code Connections tab,
and enter PlayTimelineWhenTriggered in the Custom class field.
Caution The PlayTimelineWhenTriggered class inherits from
CCNode . This is why it won't work as a custom class of a sprite node that in-
herits from CCSprite . Custom classes for sprite nodes need to inherit from
the CCSprite class. The same is true for other node types—for instance, the
custom class of a button needs to inherit from CCButton .
You should return to Xcode now to add the PlayTimelineWhenTriggered class.
Right-click the Source group and select New File . Once again, you'll go through the
dialogs in Figure 2-9 and Figure 2-10 . Name the class PlayTimelineWhenTriggered , and
make it a Subclass of CCNode before clicking Next to create the files. Open the
PlayTimelineWhenTriggered.h file, and enhance it with the code highlighted in
Listing 5-15 .
Listing 5-15 . Extending the PlayTimelineWhenTriggered class to become a TriggerDeleg-
ate
#import "CCNode.h"
#import "Trigger.h"
@interface PlayTimelineWhenTriggered : CCNode
<TriggerDelegate>
@property NSString* timelineName;
@end
Adopting the TriggerDelegate protocol is necessary to allow instances of this class
to be used as a target by the Trigger class. The timelineName property is just to al-
low more flexibility for this class.
If timelineName is nil or an empty string, the class will play the Default
Timeline when activated; otherwise, it will attempt to play the Timeline whose name is
given by timelineName . In any node where you set the
PlayTimelineWhenTriggered class as its Custom class, you can then add a