Lua templating/Snippets

This page contains some quick lua snippets to help create modules.
==General==
Get template and transcluding page arguments
local p = {}
function p.doStuff(frame)
 local transclusionArguments = frame.args
 local templateArguments = frame:getParent().args
 local templateOption = templateArguments["option"] or ""
 local transclusionOption = transclusionArguments["trans_option"] or ""
 
 return transclusionOption .. templateOption
end
 
return p
Check if a lua table contains values.
local tTab = {}
if next(tTab) then
 mw.log (true)
end
Get the title of the page that transcludes a page containing a lua invocation (parent frame). This is typically a template name.
local p = {}
function p.frameTitle(frame)
 local title = frame:getParent():getTitle()
 return (title)
end
return p
Get parameters (bool= in example) passed to template that have no value and read them to set boolean variables (or just localBool in this example).
local p = {}
 
-- include Arguments module at dev.wikia.com
local getArgs = require('Dev:Arguments').getArgs
function p.myTemplate(frame) -- Implements {{myTemplate}}
	local args = getArgs(frame, {
	trim = false,
	removeBlanks = false -- Keeps empty params
	})
	local booleanVar = false -- Default booleanVar to false
	-- Set booleanVar to true if |bool= used with template
	if args["bool"] then
		booleanVar = true
	end
	return p._myTemplate(args, booleanVar)
end
function p._myTemplate( args, isBool )
	local localBool = isBool -- Set local boolean variable 
	local returnWikitext = nil
	-- Do stuff that is conditional on isBool and set returnWikitext
	return returnWikitext
end
==Text==
Find a piece of text within text.
local textToFind = "one"
local content = "In the end there can be only one"
local startposition , endposition = string.find(content, textToFind)
if startposition then
 mw.log (true)
end
Show only a specific number of sequential tokens (group of characters) from a piece of text.
local text = "Human beings are a disease, a cancer of this planet."
local tab = mw.text.split( text, " ")
local tokens = 5
local output = ""
 for i= 0, tokens do
 output = output .. " " .. (tab[i] or "")
 end
print(output)
Output : Human beings are a disease,
==Math==
Round a number.
function p.round(num, idp)
 local roundedNumber = tonumber(string.format("%." .. (idp or 0) .. "f", num))
 return (roundedNumber)
end
==Date==
Add days to a date.
local iDays = 50
local iDayToSecs = iDays * 24 * 60 *60
local timestamp = os.time({month=12,year=2012,day=10})
local futureDate = os.date("%Y-%m-%d", timestamp + iDayToSecs)
mw.log (futureDate)
== Conditional statements ==
Using a ternary operator.
local condition = true
local trueText = "Bananas are good"
local returnText = condition and trueText or ""
--This returns trueText if condition is true, and "" if not
mw.log (returnText)
== Sorting ==
Sorting using an Associative tableSort a Table[] in Lua. http://stackoverflow.com/a/15706820
function spairs(t, order)
 -- collect the keys
 local keys = {}
 for k in pairs(t) do keys[#keys+1] = k end
 -- if order function given, sort by it by passing the table and keys a, b,
 -- otherwise just sort the keys 
 if order then
 table.sort(keys, function(a,b) return order(t, a, b) end)
 else
 table.sort(keys)
 end
 -- return the iterator function
 local i = 0
 return function()
 i = i + 1
 if keys[i] then
 return keys[i], t[keys[i]]
 end
 end
end
Usage
local power = { Majin = "11", Buu = "3", Baba = "10" , ["5"] = "ratty", ["8"] = "bum" }
-- basic usage, just sort by the keys
for k,v in spairs(power) do
 print(k,v)
end
--Sorts by keys
--Output
--5	ratty 8	bum Baba 10 Buu	3 Majin	11 
-- Sort by values
for k,v in spairs(power, function(t,a,b) return t[b] < t[a] end) do
 print(k,v)
end
-->5	 ratty
-->8	 bum
-->Buu	 3
-->Majin 11
-->Baba	 10
==See also==
* Module:Stats
* Lua templating/Converting Wikitext templates
== References ==
Category:Lua