Threading - Learn Lua for iOS Game Development - page 92

vehicle:isVehicle()
car = {}
function car:name()
print("Car")
end
car:name()
carTable= { __index = vehicle}
setmetatable(car, carTable)
car:isVehicle()
car:name()
vehicle:name()
In terms of an object-oriented language, a virtual (or abstract ) class has functions that are common,
and each object that inherits from this class (see Figure 6-1 ) has all the functions of the class.
Further, you can add more functions that are specific for the new inherited class, as shown in
Figure 6-2 .
Figure 6-1. An abstract or virtual (parent) class
Figure 6-2. An inherited or child class
In the preceding code example, we create a virtual class called vehicle and add the function
isVehicle as a member function of the class; the function prints Yes when called. Then we create a
new object called car , which has a member function called name that prints Car when called. Let's
revisit that piece of code:
vehicle = {}
function vehicle:isVehicle()
print("Yes!")
end