Lua - Retrieving button’s name from event header

To cut right to the chase, I have these two snippets of Lua code. One of which generates three buttons to put in a menu window:

for i=1,3,1 do
	local button = Button:new()
	button.minHeight = 24
	button.name = i
	local buttonText = Text:new()
	buttonText.text = "Stage "..i
	buttonText:SetAlignment(HA_CENTER, VA_CENTER)
	window:AddChild(button)
	button:SetStyleAuto()
	button:AddChild(buttonText)
	buttonText:SetStyleAuto()
	SubscribeToEvent(button, "Released", "LoadStage")
end

and later on I have that event:

function LoadStage(object, eventType, eventData)
	log:Write(LOG_INFO, "Loaded stage "..object.name)
end

In theory, this should result in the log mentioning “Loaded stage 1”, “Loaded stage 2” and “Loaded stage 3” when I press the appropiate button. However, it doesn’t work properly and pressing the buttons results in an “Execute Lua function failed: [string “init”]:61: attempt to concatenate field ‘name’ (a nil value)” error in the log. Any help?

An event handler has the signature of HandleThingy(eventType, eventData) so in your example, LoadStage is being passed a StringHash, then a VariantMap, and finally the one you call eventData is passed as nil. Inside, you are essentially trying to concatentate a field that resolves to StringHash::name, which there is no such thing.

In order to get the object sending the event, inside LoadStage you need to do something like:

function LoadStage(eventType, eventData) local e=eventData["Element"]:GetPtr("UIElement") local name=e:GetName() log:Write(LOG_INFO, "Loaded stage "..name) end

This will obtain the name of the UIElement sending the event.

Ah, I had misunderstood a few things then. Your solution works and also thanks for the explanation.