# Recursive message passing in a collection (SOLVED)

**URL:** <https://forum.defold.com/t/recursive-message-passing-in-a-collection-solved/65202>\
**Category:** Questions\
**Created:** [May 20, 2020, 12:04am UTC](https://forum.defold.com/t/recursive-message-passing-in-a-collection-solved/65202 "2020-05-20T00:04:55Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![donkeybonks](https://forum-defold.b-cdn.net/letter_avatar_proxy/v4/letter/d/f17d59/32.png) [@donkeybonks](https://forum.defold.com/u/donkeybonks)\
**Post date:** [May 20, 2020, 12:04am UTC](https://forum.defold.com/t/recursive-message-passing-in-a-collection-solved/65202/1 "2020-05-20T00:04:56Z")

</div>

Hi,  
I want to recursively update all of the things within a collection so that their “team” setting is accurate.

For example  
`coreseg.go`

```lua
go.property("team", 0)

function init(self)
	print("team is", self.team)
	msg.post(".", hash("update_team"), { team = self.team })
end

```

`segment.go`

```lua
function on_message(self, message_id, message, sender)
	if message_id == hash("update_team") then
		local tint = vmath.vector4(0, self.team/2, self.team/5, 1) -- just placeholder
		go.set("#sprite", "tint", tint)
	end
end

```

`main.script`

```lua
function init(self)
	msg.post(".", "acquire_input_focus")
	msg.post("@render:", "use_fixed_fit_projection", { near = -1, far = 1 })
	
	local rot = vmath.quat_rotation_z(0)
	
	local props1 = {}
	props1[hash("/core")] = { team = 1 }

	local props2 = {}
	props2[hash("/core")] = { team = 2 }

	collectionfactory.create("#hestiafactory", vmath.vector3(200,200,0), rot, props1)
	collectionfactory.create("#hestiafactory", vmath.vector3(300,300,0), rot, props2)
end

```

The hierarchy of the object being created by `#hestiafactory` looks like this:

 ![28%20am](https://forum-defold.b-cdn.net/uploads/default/original/3X/7/f/7f647021361e6946b49e6f9a34656db904ef8ae0.png)

But I’m only getting the message on the “core” node – I also want to see it on “segment11”, and “segment12”, “segment13” … etc however many segments I add automatically.

I sort of assumed that this was the core use-case of the message passing system.

---

<div class="post-metadata">

**Author:** ![donkeybonks](https://forum-defold.b-cdn.net/letter_avatar_proxy/v4/letter/d/f17d59/32.png) [@donkeybonks](https://forum.defold.com/u/donkeybonks)\
**Post date:** [May 20, 2020, 1:52am UTC](https://forum.defold.com/t/recursive-message-passing-in-a-collection-solved/65202/2 "2020-05-20T01:52:09Z")

</div>

Well.. I was approaching this entirely wrong. I think the documentation for Defold’s message passing system could do with some better ‘prompts’ about how to achieve certain patterns.

For example, I was approaching the problem from the idea that the parent should try and update all of its children. That was pretty futile because the most elegant way in Defold (it’s **beautiful** , btw) is for the children to just post to the parent and get a response sent directly to them. For example:

`segment.go`

```lua
function init(self)
	msg.post("core", hash("seg_created"))
end

function final(self)
	msg.post("core", hash("seg_destroyed"))
end

function update(self, dt)
	-- Add update code here
	-- Remove this function if not needed
end

function on_message(self, message_id, message, sender)
	if message_id == hash("set_team") then
		self.team = message.team
	elseif message_id == hash("set_tint") then
		go.set("#sprite", "tint", message.tint)
	end
end

```

`coreseg.go`

```lua
go.property("team", 0)

function init(self)
	-- Add initialization code here
	-- Remove this function if not needed
	print("team is", self.team)
end

function final(self)
	-- Add finalization code here
	-- Remove this function if not needed
end

function update(self, dt)
	-- Add update code here
	-- Remove this function if not needed
end

function on_message(self, message_id, message, sender)
	if message_id == hash("seg_created") then
		msg.post(sender, hash("set_team"), { team = self.team })
		msg.post(sender, hash("set_tint"), { tint = mk_segment_tint(self.team) })
	end
end

function mk_segment_tint(team)
	--local mag = math.random(0.8, 1)
	--local intensity = vmath.vector4(mag, mag, mag, 1)
	
	if team == 0 then
		return vmath.vector4(1, 1, 1, 1)
	elseif team == 1 then
		return vmath.vector4(1, 0, 1, 1)
	else
		return vmath.vector4(1, 1, 0, 1)
	end
end

```

This is pretty amazing because it handles arbitrary arrangements and depths of segments, but it’s only a few lines of code.

Now that I am more aware of the `msg.post(sender, ...)` pattern, this pretty much cleans up any concerns that I had with Defolds way of doing things.

---

<div class="post-metadata">

**Author:** ![britzl](https://forum-defold.b-cdn.net/user_avatar/forum.defold.com/britzl/32/23_2.png) [@britzl](https://forum.defold.com/u/britzl)\
**Post date:** [May 20, 2020, 10:32pm UTC](https://forum.defold.com/t/recursive-message-passing-in-a-collection-solved/65202/3 "2020-05-20T22:32:35Z")

</div>

> [@donkeybonks](#):
>
> I sort of assumed that this was the core use-case of the message passing system.

Message passing is for one-to-one messages. No broadcast out of the box, but easy to build using a Lua module if needed ([broadcast.lua](https://github.com/britzl/ludobits/blob/master/ludobits/m/broadcast.lua) and [docs](https://github.com/britzl/ludobits/blob/master/ludobits/m/broadcast.md)).

> [@donkeybonks](#):
>
> Now that I am more aware of the `msg.post(sender, ...)` pattern, this pretty much cleans up any concerns that I had with Defolds way of doing things.

Yes, it’s quite useful to have access to the `sender` to be able to “reply” if needed.