Class Functions

Just like in C++, there are two ways to define a function(method) inside a class:

• Inside class definition
• Outside class definition

Inside Class Definition

local class = ClassPP.class

local Car = class "Car" {
    Public = {
        Brand = "Lamborghini",
        getLicensePlate = function(self)
            print(self.License_Plate)
        end
    },
    Private = {
        License_Plate = "XXXX"
    }
}

In this example, we have defined a function inside the Public Access Specifier called getLicensePlate, this function when called will print the license plate of our object.

Functions inside a class will always have self as their first argument. You can think of self as a pointer to the object. You can use it to access the object itself.

Now, let's create an object from this class:

local class = ClassPP.class

local Car = class "Car" {
    Public = {
        Brand = "Lamborghini",
        getLicensePlate = function(self)
            print(self.License_Plate)
        end
    },
    Private = {
        License_Plate = "XXXX"
    }
}

local newCar = Car.new()
newCar:getLicensePlate()

You can notice that instead of calling the function with . operator, we used : operator. This is because of the first argument always being self. Calling the function with a . operator will cause the self to not exist, so you must either call the function with the object as its first argument, or use : operator, as it makes it easier.

Functions with multiple parameters

local class = ClassPP.class

local Car = class "Car" {
    Public = {
        Brand = "Lamborghini",
        getLicensePlate = function(self, number)
            print(self.License_Plate, number) -- Prints "XXXX 1"!
        end
    },
    Private = {
        License_Plate = "XXXX"
    }
}

local newCar = Car.new()
newCar:getLicensePlate(1) -- Calling the function with an argument

Like in this example, you can call functions with multiple parameters.
Since self is the first argument, all the other arguments that come after will start at 2. This will be important in later pages.

Outside Class Definition

To define a function outside of the class, you must define it as:
function Class.<accessSpecifier>:<functionName>

local class = ClassPP.class

local Car = class "Car" {
    Public = {
        Brand = "Lamborghini",
    },
    Private = {
        License_Plate = "XXXX"
    }
}

function Car.Public:getLicensePlate(number)
    print(self.License_Plate, number) -- Prints "XXXX 1"!
end

local newCar = Car.new()
newCar:getLicensePlate(1)

In this example, we defined a function outside of the class by specifying the class name, then the access specifier, followed by the : operator and the name of the function. Unlike in C++, you do not have to define the function first inside the class to use this method.

Info

Outside Class Definition syntax is recommended as it allows for a better formatting style.