NPCs and Associated Technology - Creating E-Learning Games with Unity - page 159

3. Add a public reference to npcCondition and npcResponse . Whenever
this condition evaluates to true , the interaction class will dispatch the re-
sponse:
public npcCondition condition;
public npcResponse response;
4. We also add an activated Boolean to allow us to selectively enable and dis-
able interactions based on the state of the game:
public bool active;
5. The method eval() is where the brunt of the work in the interaction class
is performed. It first checks if the interaction is active. If it is, and if there is
a condition, it will evaluate the condition and check if that condition is true or
not:
if (active == true)
{
if (condition != null)
{
if (condition.eval() == true)
{ ...
6. Recall that the npcCondition reference could be any specialization of
npcCondition so that the implementation of the eval() function could ap-
pear in any child class as long as it has been assigned in the inspector.
7. If the condition returns true , we check if a response class has been associ-
ated in the inspector. If it has been dispatched, we dispatch the response!
if (response != null)
rval = response.dispatch();
Congratulations! We have implemented a container class that associates a generic
condition with a generic response. We use the abstract keyword in the base class so
that child classes that derive from npcCondition and npcResponse can all freely
be connected to npcInteraction . Now let's look at how to connect our interac-
tions together.