RX + Defold

The Defoldmine
#1

Make some experiments with RxLua and defold.

Rx it is a reactive programming. You can read more here http://reactivex.io/.

Rx is based on Observables , Observers, and Operators

An Observer essentially subscribes to an Observable.

The Observable then emits streams of data which the Observer listens and reacts to, setting in motion a chain of operations on the data stream. The real power comes from Operators or “Reactive Extensions” (hence the term Rx) .

Operators allow you to transform, combine, manipulate, and work with the sequences of items emitted by Observables.

My problem
I like mvc and observable pattern. But it hard to use it in defold, because when i worked with go or gui, i need to worked inside it context. I can’t subscribe in gui to model,and change gui when model change event emmited(yes i can, save events and then iterate them on_update, i have lib for that, but it is not comfortable.
I can use messages for it, but messages worked only with go/gui, not with lua modules(i can make module that will be emmit messages for modules, but it is not very comfortable).Also working with messages not very comfortable =)

RXLua
I add 2 methods to RxLua lib.
go and go_distinct. They worked in context of go.
go emmits all events
go_distinct only unique per frame.

Go is very simple. It emmits events when scheduler will be updated.I update it every frame in context of go.

function  Observable:go(scheduler)
    return self:delay(0,scheduler)
end

Rx Example
Model(emmit 5 equals events every frame)

function M:initialize()
	self.rx = RX.Subject()
end

local frame = 0
function M:update(dt, no_save)
	self.ecs_world:update(dt)
	for i=1,5 do
		self.rx:onNext(frame)
	end
	frame = frame + 1
end

Subscription go script

...
    WORLD.rx:go(SCHEDULER):subscribe(function(v)
        print("all:" .. v)
    end)
    WORLD.rx:go_distinct(SCHEDULER):subscribe(function(v)
        print("distinct:" .. v)
    end)
...

function Scene:update(go_self, dt)
    SCHEDULER:update(dt)
end

DEBUG:SCRIPT: [INFO 11:01:02] none: /scenes/logo/logo_scene.lua:21: distinct:45
[5]DEBUG:SCRIPT: [INFO 11:01:02] none: /scenes/logo/logo_scene.lua:18: all:45

I don’t show here power of Rx. When you can:receive value, change it, mix it with other and etc. It contains a lot of methods, you can read it in docs https://github.com/bjornbytes/RxLua/tree/master/doc.

When you read it, you can think that rx complex and redundant. But give it a chance.It is simple but powerful tool. I love it = )

Project
It contains a lot of code, because i use my template for all project. You need
libs/rx
world/world.lua (model of world)
init_controller(update world model)
scenes/logo/logo_scene.lua.(scene controller.Subscribe to world)

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Feedback after gamejam
#2

Hi @d954mas nice post, I would like to pass functions inside on_message Defold functions, but it’s not possible, so I search more about it and find RXlua, but not clear how to add inside Defold. I try the dependencies link and fetch but not load, I’m new in Defold still not sure how to make it work.

1 Like
#3

Hi, it is not defold library. It is lua library, you need copy lua file.

Not sure how it help you to pass functions, but you can try.

Also look at flow https://github.com/britzl/ludobits
Maybe it will be better work for you

1 Like
#4

Hi @d954mas I try the"ludobits.m.broadcast" but dont work like I spected
I atach the script_1 at 3 gameobjects.

--script_1
local broadcast = require "ludobits.m.broadcast"

function init(self)
	broadcast.register("foo")
end

function final(self)
	broadcast.unregister("foo")
end

function on_message(self, message_id, message, sender)
	if message_id == hash("foo") then
		pprint(message)
	end
end

and script_2 to one game object.

--script_2
local broadcast = require "ludobits.m.broadcast"

function init(self)
	broadcast.send("foo", { something = 123 })
end

I subscribe to the message “foo” in all 3 game objects, when send the message the code execute one time, instead of 3 times. Did you know why don’t execute the same message 3 times?

#5

The order in which init() is called is not guaranteed. In your case the init() of script_1 has probably been run on 1 game object. Then you hit the init() of script_2 where you broadcast a message. And this will happen immediately, before the init() of the other two game objects using script_1.

If you really want to broadcast something in init() you need to delay it. You can use a timer to delay it:

function init(self)
	-- delay until immediately after all init() functions have been run
	timer.delay(0, false, function()
		broadcast.register("foo")
	end)
end
1 Like