Example of state bags usage in FiveM (Siren system for vehicles)

c_siren.lua

local sirens = {}
local function playSiren(entity)
    -- Prevent from playing siren twice
    if sirens[tostring(entity)] then return false end
    print('Play siren', 'State', Entity(entity).state['siren'])
    sirens[tostring(entity)] = true
    return true
end
local function stopSiren(entity)
    sirens[tostring(entity)] = nil
    print('Stop siren', 'State', Entity(entity).state['siren'])
end

AddStateBagChangeHandler('siren', nil, function(bagName, key, value, _, rep)
    -- Handle only siren 'on' state
    if value ~= true then return end

    -- Get entity (stable alternative for GetEntityFromStateBagName(bagName))
    local netId, _ = string.gsub(bagName, 'entity:', '')
    netId = tonumber(netId)
    local timeoutAt = GetGameTimer() + 1500
    while not NetworkDoesEntityExistWithNetworkId(netId) do
        Wait(0)
        if GetGameTimer() >= timeoutAt then
            return print('Timeout, entity network doesnt exist', netId)
        end
    end
    local entity = NetworkGetEntityFromNetworkId(netId)

    -- Ensure entity exists
    if not DoesEntityExist(entity) then return print('Entity doesnt exist', entity) end

    -- Ensure handler executed only once (local player replication)
    local amOwner = NetworkGetEntityOwner(entity) == PlayerId()
    if amOwner and replicated then return end

    -- Ensure entity has the state assigned
    while Entity(entity).state['siren'] ~= true do Wait(0) end

    -- Play siren
    if playSiren(entity) then
        -- Wait entity exists and while siren is enabled
        while DoesEntityExist(entity) and Entity(entity).state['siren'] == true do
            Wait(200)
        end
    
        -- Stop siren
        stopSiren(entity)
    end
end)

RegisterCommand('sirenon', function()
    local vehicle = GetVehiclePedIsIn(PlayerPedId())
    if not DoesEntityExist(vehicle) then
        return
    end
    Entity(vehicle).state:set('siren', true, true)
end, false)

RegisterCommand('sirenoff', function()
    local vehicle = GetVehiclePedIsIn(PlayerPedId())
    if not DoesEntityExist(vehicle) then
        return
    end
    Entity(vehicle).state:set('siren', false, true)
end, false)