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Inheriting Classes

How to inherit nanos world Classes. nanos world provides a built-in way of inheriting the built-in Classes

caution

This feature is still experimental, you can try it out and provide feedback before it's full release!

Inheriting a Class

Inheriting a nanos world Class is really easy, for that you just need to use the Inherit static method on the Class you want to inherit:

-- Creates a new Class called "MyNewClass" inheriting from Prop
-- and stores it in the variable MyNewClass
MyNewClass = Prop.Inherit("MyNewClass")

-- Spawn it using the default constructor
local my_new_class_instance = MyNewClass(Vector(), Rotator(), "nanos-world::SM_Cube")

Multiple Inheritance

You can also inherit from other inherited classes:

-- Creates a new Class called "MyNewSubClass" inheriting from MyNewClass
MyNewSubClass = MyNewClass.Inherit("MyNewSubClass")

-- Spawn it using the default constructor
local instance = MyNewSubClass(Vector(), Rotator(), "nanos-world::SM_Cube")

Overriding the Constructor

You can create your own Constructor for your entities, for that you need to define the Constructor method:

-- Defines my constructor with any parameters you desire
function MyNewClass:Constructor(location, rotation)
-- Do any kind of logic here
location = location + Vector(0, 0, 100)

-- Calls Super Constructor to finalize the construction
-- This is the original constructor (in this case from Prop)
-- This is mandatory, if you don't call it, it will throw an error
-- You will only be able to access original and your own class
-- methods after calling it, when the class is completely spawned
self.Super:Constructor(location, rotation, "nanos-world::SM_Cube")

-- Now it's allowed to class methods
self:SetMaterialColorParameter("Tint", Color.RED)
end

-- Spawn it using your custom constructor
local my_new_class_instance = MyNewClass(Vector(123, 456, 100), Rotator())
tip

Inside the constructor, the entity is not fully spawned yet, so you cannot call other entity methods besides self.Super:Constructor. Here you should just use to validate constructor parameters, and use Spawn event to fully setup the entity.

Global Registry

Through the parent class, we can get a list of all children classes of that class, having a global registry of all existing classes!

local children_classes = ToolGun.GetInheritedClasses()
for _, class in pairs(children_classes) do
-- 'class' is a custom inherited class! we can spawn it
local p = class()
end

Adding new Methods

Adding new methods for new classes is very straightforward, let's say we want to add a new method for MyNewClass, we just do that:

function MyNewClass:Explode()
-- Spawns a particle
Particle(self:GetLocation(), Rotator(), "nanos-world::P_Explosion")

-- Destroys myself
self:Destroy()
end
tip

Within your methods, you can access the called entity instance with self.

And then you are able to call it as usual:

my_new_class_instance:Explode()

Overriding Existing Methods

Besides creating new methods, it's possible to override existing ones, for that just redefine them:

function MyNewClass:SetLocation(new_location)
-- Do any kind of logic here
new_location = new_location + Vector(0, 0, 100)

-- Call Super to set the location to the parent Prop
self.Super:SetLocation(new_location)
end

Calling Native Methods

To call native Class methods, you can use the special variable self.Super, which will allow you accessing the native and original methods directly:

function MyNewClass:GetRotation()
-- Calls original GetRotation and adds 90 to yaw
return self.Super:GetRotation() + Rotator(0, 90, 0)
end

Calling Parent Methods

Besides calling the original/native method with self.Super, we can also call parent methods if you have nested inheritance.

For that, you must use a special Lua syntax with PARENT_CLASS.METHOD_NAME(self, ...), for example:

tip

In Lua, passing a value as the first parameter to a method while calling it with . will make that value appear as self inside the called method (if the method was defined with :).

-- Inherits Prop
MyNewClass = Prop.Inherit("MyNewClass")

function MyNewClass:SetScale(scale)
-- Does some logic
scale = scale * 2

-- Calls Super (original Prop method)
self.Super:SetScale(scale) * 2
end

-- Inherits MyNewClass
MyNewSubClass = MyNewClass.Inherit("MyNewSubClass")

function MyNewSubClass:SetScale(scale)
-- Does some logic
scale = scale + Vector(2, 2, 2)

-- Calls Parent MyNewClass method with special syntax
MyNewClass.SetScale(self, scale)
end
tip

This same rule applies for calling inherited Constructors!

Overriding __newindex

It is also possible to add a custom __newindex metamethod on Inherited Classes.

tip

__newindex metamethod is a function which is triggered when you attempt to set a value in an entity. E.g.: my_entity.something = 123.

For that, we just add a custom method called newindex:

note

The method name must be newindex and not __newindex as __newindex is the native method used internally to make the inheritance to work.

function MyNewClass:newindex(key, value)
Console.Log("Setting a %s value: %s = %s", tostring(self), key, tostring(value))
end

An useful way of using __newindex is overriding it to SetValue automatically:

function MyNewClass:newindex(key, value)
self:SetValue(key, value)
end

-- Example usage
local my_entity = MyNewClass()
my_entity.amazing_value = 123

Overriding __index

tip

__index metamethod is a function which is triggered when you attempt to get a value from an entity. E.g.: local value = my_entity.something.

For that, we just add a custom method called index:

note

The method name must be index and not __index as __index is the native method used internally to make the inheritance to work.

function MyNewClass:index(key)
Console.Log("Getting %s value: %s", tostring(self), key)
-- ... do something
return some_value
end

You can also use __index to return a method:

function MyNewClass:index(key)
Console.Log("%s key not found: %s", tostring(self), key)

-- inside the redirected method you will have all the parameters passed originally
return function(self, param1, param2...)
-- ... do something
return "triggered!"
end

-- or you can even redirect to other member functions
return MyClass.SetLocation
end

local my_entity = MyNewClass()
my_entity:NonExistentMethod(123, "456")

An useful way of using __index is overriding it to GetValue automatically:

function MyNewClass:index(key)
return self:GetValue(key)
end

local my_entity = MyNewClass()
local amazing_value = my_entity.amazing_value

Overriding __tostring

You can override __tostring as well as usual:

function MyNewClass:__tostring()
return "My Incredible Class!"
end

Native Events

All events which are triggered on an inherited Class will only trigger in that Class and it's parents, also the parameter passed is the custom entity itself, example:

Prop.Subscribe("Spawn", function(self)
Console.Log("Spawned Prop: %s", tostring(self))
end)

MyNewClass.Subscribe("Spawn", function(self)
Console.Log("Spawned MyNewClass: %s", tostring(self))
end)

local my_entity = MyNewClass()
local my_prop = Prop()
local my_other_entity_inherited_from_prop = MyOtherClass()

-- Will output:
-- Spawned Prop: MyNewClass
-- Spawned MyNewClass: MyNewClass
-- Spawned Prop: Prop
-- Spawned Prop: MyOtherClass

Another way of subscribing is separating the definition and the subscription, this way you don't need the first self parameter anymore:

function MyNewClass:OnSpawn()
-- self is present is this context automatically
Console.Log("Spawned MyNewClass: %s", tostring(self))
end

MyNewClass.Subscribe("Spawn", MyNewClass.OnSpawn)

Multiple Parents Example:

MyNewClass = Prop.Inherit("MyNewClass")
MyNewSubClass = MyNewClass.Inherit("MyNewSubClass")
MyNewOtherSubClass = MyNewClass.Inherit("MyNewOtherSubClass")

Prop.Subscribe("Spawn", function(self)
Console.Log("Spawned Prop: %s", tostring(self))
end)

MyNewClass.Subscribe("Spawn", function(self)
Console.Log("Spawned MyNewClass: %s", tostring(self))
end)

MyNewSubClass.Subscribe("Spawn", function(self)
Console.Log("Spawned MyNewSubClass: %s", tostring(self))
end)

MyNewOtherSubClass.Subscribe("Spawn", function(self)
Console.Log("Spawned MyNewOtherSubClass: %s", tostring(self))
end)

local my_entity = MyNewSubClass()

-- Will output:
-- Spawned Prop: MyNewClass
-- Spawned MyNewClass: MyNewClass
-- Spawned MyNewSubClass: MyNewClass
tip

Note that Prop and all parent Classes will still trigger events for all child Classes!

Client/Server Synchronization

If you define your entities on both Client and Server side, they will behave properly and in a synchronized way! Example:

Server/Index.lua
MyNewClass = Prop.Inherit("MyNewClass")

MyNewClass.Subscribe("Spawn", function(self)
Console.Log("Spawned MyNewClass: %s", tostring(self))
end)

local my_entity = MyNewClass()

-- Will output:
-- Spawned MyNewClass: MyNewClass
Client/Index.lua
MyNewClass = Prop.Inherit("MyNewClass")

MyNewClass.Subscribe("Spawn", function(self)
-- It was spawned on server and will spawn on Client as a MyNewClass properly
Console.Log("Spawned MyNewClass: %s", tostring(self))
end)

-- Will output:
-- Spawned MyNewClass: MyNewClass

Custom Remote Events

It is also possible to trigger custom events on remote instances of your Class, using the methods CallRemoteEvent or BroadcastRemoteEvent, it works like the Events class:

Client/Index.lua
-- inherits the Class
MyNewClass = Prop.Inherit("MyNewClass")

-- defines a custom method
function MyNewClass:OnMyCustomRemoteEvent(a, b)
Console.Log("OnMyCustomRemoteEvent!", tostring(self), a, b)
self:CallRemoteEvent("AnotherRemoteEvent", 456, "def")
end

-- subscribes for a custom remote event
MyNewClass.SubscribeRemote("MyCustomRemoteEvent", MyNewClass.OnMyCustomRemoteEvent)
Server/Index.lua
-- inherits the Class
MyNewClass = Prop.Inherit("MyNewClass")

-- Note that server-side received remote events have the 'player as first parameter
function MyNewClass:OnAnotherRemoteEvent(player, a, b)
Console.Log("OnAnotherRemoteEvent!", tostring(self), tostring(player), a, b)
end

-- subscribes for a custom remote event
MyNewClass.SubscribeRemote("AnotherRemoteEvent", MyNewClass.OnAnotherRemoteEvent)

-- spawns an entity and calls the custom remote event on that entity
local p = MyNewClass(...)
p:BroadcastRemoteEvent("MyCustomRemoteEvent", 123, "abc")

Class Custom Default Values

It is possible to set a list of default values to the Inherited Class when creating it, just pass it as the 2nd parameter to Inherit:

-- inherits the Class
MyNewClass = Prop.Inherit("MyNewClass", {
name = "My Name",
category = "breakable",
my_custom_param = 123
})

Console.Log(MyNewClass.category)
-- outputs "breakable"

Class Register Event

When you inherit a new class, the event ClassRegister will be triggered on the parents classes, allowing Packages to know when a new Class is registered.

Prop.Subscribe("ClassRegister", function(class)
-- here we see an useful case for the default values
-- as we can access it here
Console.Log(MyNewClass.name) -- outputs "My Name
-- now we can do something (add to spawn menu?)
end)

-- inherits the Class
MyNewClass = Prop.Inherit("MyNewClass", {
name = "My Name",
category = "breakable",
my_custom_param = 123
})