Workshop

Quiz

1:	We did not want our Command::execute() method to be overridden by code in child classes. How did we enforce this?
2:	Briefly, how did we ensure that there was only one DataStore object in our system at any one time?
3:	We said that the practice of a method calling and using abstract methods defined in the same class was an example of a design pattern. What was its name?
4:	Which keyword did we use to check that an object we had instantiated belonged to the Command family?
5:	How did we ensure that our Command class status flags were unchangeable and available via the class rather than particular object instances?

Answers

A1:	You can prevent a child class from overriding a method by declaring it final.
A2:	We made the DataStore object a Singleton. That is, we made its constructor private so a DataStore object could be instantiated only by a static method in the DataStore class itself. The static method can ensure that it returns only the same single instance of a DataStore object when it is called.
A3:	A method calling and using abstract methods defined in the same class is an example of the template method pattern.
A4:	We can use instanceof to test the type of an object.
A5:	You can declare constant properties with the const keyword. A constant property is unchangeable at runtime and is available via the class rather than object instances.