Lua/Tutorials/A tank that shoots tanks

In this tutorial, we'll explore uses for network events and vehicle spawning. Also, a tank that shoots tanks. Who doesn't love metatanks?

Server

function PlayerChat(args)
	-- Spawn a tank and put them inside it.
	if args.text == "/metatank" then
		spawnArgs = {}
		spawnArgs.model_id = 56 -- Razorback
		spawnArgs.position = args.player:GetPosition()
		spawnArgs.angle = args.player:GetAngle()
 
		local vehicle = Vehicle.Create(spawnArgs)
		args.player:EnterVehicle(vehicle, VehicleSeat.Driver)
 
		return false
	end
 
	return true
end
Events:Subscribe("PlayerChat", PlayerChat)
 
function SpawnTankBullet(args, player)
	-- Make sure their vehicle still exists.
	local vehicle = player:GetVehicle()
	if not IsValid(vehicle) then
		return
	end
 
	spawnArgs = {}
	spawnArgs.model_id = 56
	spawnArgs.position = vehicle:GetPosition() + Vector3(0, 2, 0) + args.direction * 15
	spawnArgs.angle = args.angle
	spawnArgs.linear_velocity = args.direction * 100
 
	Vehicle.Create(spawnArgs)
end
Network:Subscribe("FireTank", SpawnTankBullet)

Client

timer = nil
fireInterval = 1
 
function Fire()
	local args = {}
	args.angle = Camera:GetAngle()
	args.direction = args.angle * Vector3(0, 0, -1)
 
	Network:Send("FireTank", args)
end
 
function TryToFire()
	-- Make sure we only fire once every fireInterval. Otherwise, it would try to spam network
	-- messages every frame. That is not good.
	if timer then
		if timer:GetSeconds() >= fireInterval then
			timer = nil
		end
	else
		Fire()
		timer = Timer()
	end
end
 
function LocalPlayerInput(args)
	-- We only want the Razorback tank.
	local vehicle = LocalPlayer:GetVehicle()
	if vehicle == nil or vehicle:GetModelId() ~= 56 then
		return true
	end
	-- Replace the vehicle fire actions with our own implementation.
	if args.input == Action.VehicleFireRight or args.input == Action.VehicleFireLeft then
		TryToFire()
		return false
	else
		return true
	end
end
Events:Subscribe("LocalPlayerInput", LocalPlayerInput)

As you can see, the client uses Network:Send with a table as its second argument. The server receives the event with the table, and the player who sent the network event.

Flaws

This is just a simple example and can be improved upon greatly:

• The tanks do not despawn.
• Any Razerback tank will work, not just ones you create.
• The firing limit is imposed on the client, not the server.
  • Never trust the client. It's possible they could cheat and fire dozens of tanks per second at any position they wish.