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Lua scripts end in the <code>.lua</code> extension & are stored in the <code>data/script</code> directory.
 
= Lua Basics =
== Objects and Functions ==
 
For more detailed information, see the [https://www.lua.org/docs.html Lua reference manual].
The following objects & functions are exposed to the Lua engine:
 
=== luajavaComments ===
 
Lua uses double dashes (<code>--</code>) for single line comments & double dashes followed by double square brackets (<code>[[</code>) & closed with double square brackets (<code>]]</code>) for multi-line comments:
This is an object of the LuajavaLib library. It can be used to coerce Java static objects to Lua or create new Java object instances.
<pre>
-- a single line comment
 
--[[
a multi-line comment
]]
</pre>
 
== Variables ==
 
By default, Lua variables are set in [https://en.wikipedia.org/wiki/Global_variable '''global''' scope] (meaning it is exposed to the entire Lua engine). To create a variable in [https://en.wikipedia.org/wiki/Local_variable '''local''' scope], the <code>local</code> keyword must be used:
Example of exposing a static object & enums to Lua:
<pre>
-- store a Java enum in a Lua global variable
var1 = "Hello world!"
ConversationStates = luajava.bindClass("games.stendhal.server.entity.npc.ConversationStates")
 
-- a local variable
-- access the enum values like so
local var2 = "Hello world!"
ConversationStates.IDLE
</pre>
 
== Data Types ==
Example of creating an object instance:
 
Some common data types in Lua are ''string'', ''integer'', ''boolean'', & ''table''. Type names do not need to be declared when setting variables.
 
Examples:
<pre>
-- store instance in localstring variable
local var1 = "Hello world!"
local dog = luajava.newInstance("games.stendhal.server.entity.npc.SilentNPC")
-- access object methods like so
dog:setEntityClass("animal/puppy")
dog:setPosition(2, 5)
 
-- integer variable
-- class with constructor using parameters
local var2 = 11
local speaker = luajava.newInstance("games.stendhal.server.entity.npc.SpeakerNPC", "Frank")
 
speaker:setOutfit("body=0,head=0,eyes=0,hair=5,dress=5")
-- boolean variable
speaker:setPosition(2, 6)
local var3 = true
 
-- table variable
local var4 = {}
</pre>
 
=== Strings ===
To make scripting easier, Stendhal employs a {{StendhalFile|master|src/games/stendhal/server/core/scripting/lua/init.lua|master script}} & some helper objects & methods to handle the functionality mentioned above. An explanation of these objects & methods follows.
 
==== gameString Concatenation ====
 
String concatenation is simple, much like Java uses a plus operator (<code>+</code>) to join strings, Lua uses two periods (<code>..</code>).
The main object that handles setting zone & adding entities to game.
 
Example:
Methods:
<pre>
* <code>game:add(object)</code> - Adds an object to the current zone.
-- create a string variable
* <code>game:setZone(name)</code> - Sets the current zone.
local var = "Hello"
* <code>game:createSign(visible)</code> - Creates a new {{StendhalFile|master|src/games/stendhal/server/entity/mapstuff/sign/Sign.java|Sign}} instance.
* <code>game:createShopSign(name, title, caption, seller)</code> - Creates a new {{StendhalFile|master|src/games/stendhal/server/entity/mapstuff/sign/ShopSign.java|ShopSign}} instance.
 
-- append another string
=== npcHelper ===
var = var .. " world!"
 
print(var) -- prints "Hello world!"
This object helps to create instances of {{StendhalFile|master|src/games/stendhal/server/entity/npc/SpeakerNPC.java|SpeakerNPC}} & {{StendhalFile|master|src/games/stendhal/server/entity/npc/SilentNPC.java|SilentNPC}} classes.
</pre>
 
=== Tables ===
Methods:
* <code>npcHelper:createSpeakerNPC(name)</code> - Creates a new SpeakerNPC.
* <code>npcHelper:createSilentNPC()</code> - Creates a new SilentNPC.
* <code>npcHelper:setPath(npc, path, loop)</code> - Sets the path for the specified NPC.
* <code>npcHelper:setPathAndPosition(npc, path, loop)</code> - Sets the path & starting position of the specified NPC.
* <code>npcHelper:addMerchant(merchantType, npc, items, offer)</code> - Adds merchant behavior to <code>npc</code> of either a buyer or seller defined by <code>merchantType</code>.
* <code>npcHelper:addSeller(npc, items, offer)</code> - Adds seller merchant behavior to <code>npc</code>.
* <code>npcHelper:addBuyer(npc, items, offer)</code> - Adds buyer merchant behavior to <code>npc</code>.
 
A Lua table is a data type similar to a Java list or map. Tables can be indexed or use key=value pairs.
== Setting Zone ==
 
''(<span style="color:red;">IMPORTANT NOTE: Lua table indexes begin at 1, not 0</span>)''
 
==== Creating Tables ====
 
An empty table is initialized with a pair of curly braces (<code>{}</code>):
<pre>
local mytable = {}
</pre>
 
You can add values to indexed tables at initialization or with the <code>table.insert</code> method:
<pre>
-- create a table with values
local mytable = {"foo"}
 
-- add value
table.insert(mytable, "bar")
</pre>
 
To create a key=value table, any of the following methods can be used to add values:
<pre>
-- all of these do the same thing, that is, assigning "bar" to mytable.foo
local mytable {
foo = "bar",
["foo"] = "bar",
}
mytable.foo = "bar"
mytable["foo"] = "bar"
</pre>
 
==== Accessing Table Values ====
 
Square brackets (<code>[]</code>) enclosing an index number are used to access values in indexed tables (''remember that Lua table indexes start at "1" not "0"''):
<pre>
local mytable = {"foo", "bar"}
 
print(mytable[1]) -- prints "foo"
print(mytable[2]) -- prints "bar"
</pre>
 
In a key=value table, values can be accessed by either enclosing the key string in square brackets or concatenating the key member using a <code>.</code>:
<pre>
local mytable = {foo="bar"}
 
-- using square brackets
print(mytable["foo"]) -- prints "bar"
 
-- using concatenated member
print(mytable.foo) -- prints "bar"
</pre>
 
==== Iterating Tables ====
 
Tables can be iterated in a <code>for</code> loop using the <code>pairs</code> or <code>ipairs</code> iterators. Loops are terminated with the <code>end</code> keyword:
<pre>
local mytable = {"foo", "bar"}
 
print("indexes:")
for idx in pairs(mytable) do
print(idx)
end
 
print("\nvalues:")
for idx, value in pairs(mytable) do
print(value)
end
</pre>
 
Output:
<pre>
indexes:
1
2
 
values:
foo
bar
</pre>
 
Using a key=value table:
<pre>
local mytable = {
["foo"] = "hello",
["bar"] = " world!",
}
 
print("keys:")
for key in pairs(mytable) do
print(key)
end
 
print("\nvalues:")
for key, value in pairs(mytable) do
print(value)
end
</pre>
 
Output:
<pre>
keys:
foo
bar
 
values:
hello
world!
</pre>
 
See also: [http://lua-users.org/wiki/TablesTutorial Lua Tables Tutorial]
 
=== Functions ===
 
Like normal variables, functions can be declared as '''global''' or '''local''' & must be terminated with the <code>end</code> keyword.
 
There are two ways to define functions with the <code>function</code> keyword:
<pre>
local function myFunction()
print("Hello world!")
end
</pre>
 
or
<pre>
local myFunction = function()
print("Hello world!")
end
</pre>
 
Functions can also be members of a table:
<pre>
local myTable = {}
function myTable.myFunction()
print("Hello world!")
end
</pre>
 
or
<pre>
local myTable = {}
myTable.myFunction = function()
print("Hello world!")
end
</pre>
 
or
<pre>
local myTable = {
myFunction = function()
print("Hello world!")
end,
}
 
-- execute with
myTable.myFunction()
</pre>
 
== Comparison Operators ==
 
{| class="wikitable"
|+ Logical Operators
! Operator !! Description !! Java Equivalent
|-
| and || logical ''and'' || &&
|-
| or || logical ''or'' || <nowiki>||</nowiki>
|-
| not || logical ''opposite'' || !
|}
 
{| class="wikitable"
|+ Relational Operators
! Operator !! Description !! Java Equivalent
|-
| < || less than || <
|-
| > || greater than || >
|-
| <= || less than or equal to || <=
|-
| >= || greater than or equal to || >=
|-
| == || equal to || ==
|-
| ~= || not equal to || !=
|}
 
= Stendhal Application =
 
== Zones ==
 
=== Setting Zone ===
 
To set the zone to work with, use the <code>game</code> object:
Line 71 ⟶ 270:
</pre>
 
=== Create New Zone ===
The logger is exposed to Lua via the <code>logger</code> object:
 
It is recommended to create new zones in the XML configurations in {{StendhalFile|master|data/conf/zones|data/conf/zones}}.
 
Currently creating new zones via Lua is not supported.
 
=== Add Zone Music ===
 
Music can be added to zones with the <code>game:setMusic</code> function. It supports the following arguments:
* <span style="color:darkgreen; font-style:italic;>filename:</span> Basename of the OGG audio file to use stored in {{StendhalFile|master|data/music|data/music}}.
* <span style="color:darkgreen; font-style:italic;>args:</span> A table of key=value integers.
* Valid keys:
** <span style="color:darkblue; font-style:italic;">volume:</span> Volume level (default: 100).
** <span style="color:darkblue; font-style:italic;">x:</span> The horizontal point for the source of the music (default: 1).
** <span style="color:darkblue; font-style:italic;">y:</span> The vertical point for the source of the music (default: 1).
** <span style="color:darkblue; font-style:italic;">radius:</span> The radial range at which the music can be heard (default: 10000).
 
Example:
<pre>
if game:setZone("0_semos_plains_n") then
local zone = "0_semos_city"
game:setMusic("pleasant_creek_loop", {volume=85, radius=100})
if game:setZone(zone) then
-- do something
else
logger:error("Could not set zone: " .. zone)
end
</pre>
Line 86 ⟶ 298:
=== Signs ===
 
Signs can be created with <code>gameentities:createSign</code> and <code>gameentities:createShopSign</code>:
 
<pre>
Line 92 ⟶ 304:
if game:setZone(zone) then
-- create the sign instance
local sign = gameentities:createSign()
sign:setEntityClass("signpost")
sign:setPosition(12, 55)
Line 106 ⟶ 318:
=== NPCs ===
 
Use the <code>gameentities:createSpeakerNPC</code> method to create an interactive NPC:
 
<pre>
Line 112 ⟶ 324:
if game:setZone(zone) then
-- Use helper object to create a new NPC
local npc = npcHelperentities:createSpeakerNPC("Lua")
npc:setEntityClass("littlegirlnpc")
npc:setPosition(10, 55)
Line 125 ⟶ 337:
}
 
npc:setPath(nodes)
-- Use helper object to create NPC path
npcHelper:setPath(npc, nodes)
 
-- Dialogue
Line 137 ⟶ 348:
logger:error("Could not set zone: " .. zone)
end
</pre>
 
==== Adding Transitions ====
 
A simple example of adding a chat transition can be done without any special functionality:
<pre>
local frank = entities:createSpeakerNPC("Frank")
frank:add(ConversationStates.IDLE,
ConversationPhrases.GREETING_MESSAGES,
nil,
ConversationStates.ATTENDING,
"Hello.",
nil)
</pre>
 
This simply adds a response to saying "hello" & sets the NPC to attend to the player (equivalent of <code>frank:addGreeting("Hello")</code>).
 
For more complicated behavior, we need to use some helper methods. If we want to check a condition we use the <code>conditions:create</code> method. The first parameter is the string name of the ChatCondition we want to instantiate. The second parameter is a table that contains the values that should be passed to the ChatCondition constructor.
 
Example:
<pre>
frank:add(ConversationStates.IDLE,
ConversationPhrases.GREETING_MESSAGES,
conditions:create("PlayerHasItemWithHimCondition", {"money"}),
ConversationStates.ATTENDING,
"Hello.",
nil)
</pre>
 
In this scenario, the NPC will only respond if the player is carrying <item>money</item>.
 
A NotCondition instance can be created with the <code>actions:notCondition</code> method:
 
Example usage:
<pre>
local condition = conditions.notCondition(conditions:create("PlayerHasItemWithHimCondition", {"money"})
</pre>
 
To add a ChatAction, we use the <code>actions:create</code> method. Its usage is identical to <code>conditions:create</code>.
 
Example:
<pre>
frank:add(ConversationStates.IDLE,
ConversationPhrases.GREETING_MESSAGES,
conditions:create("PlayerHasItemWithHimCondition", {"money"}),
ConversationStates.ATTENDING,
"Hello.",
actions:create("NPCEmoteAction", {"looks greedily at your pouch of money.", false}))
</pre>
 
Lua tables can be used to add multiple conditions or actions:
<pre>
frank:add(ConversationStates.IDLE,
ConversationPhrases.GREETING_MESSAGES,
{
conditions:create("PlayerHasItemWithHimCondition", {"money"}),
conditions:notCondition(conditions:create("NakedCondition")),
},
ConversationStates.ATTENDING,
nil,
{
actions:create("SayTextAction", {"Hello."}),
actions:create("NPCEmoteAction", {"looks greedily at your pouch of money.", false}),
})
</pre>
 
In this scenario, the NPC will respond if the player has money & is not naked.
 
Nested tables are supported as well:
<pre>
local conditions = {
conditions:create("PlayerHasItemWithHimCondition", {"money"}),
{
conditions:notCondition(conditions:create("NakedCondition")),
},
}
 
frank:add(ConversationStates.IDLE,
ConversationPhrases.GREETING_MESSAGES,
conditions,
ConversationStates.ATTENDING,
nil,
{
actions:create("SayTextAction", {"Hello."}),
actions:create("NPCEmoteAction", {"looks greedily at your pouch of money.", false}),
})
</pre>
 
==== Adding Merchant Behavior ====
 
The <code>merchants</code> object is used for adding merchant behavior (buying/selling) to an NPC.
Merchant behavior ''(buying/selling)'' can be set with one of the following helper functions:
* ''npcHelper:addMerchant(merchantType, npc, prices, addOffer)''
* ''npcHelper:addBuyer(npc, prices, addOffer)''
* ''npcHelper:addSeller(npc, prices, addOffer)''
** Arguments:
*** ''merchantType:'' (string) If set to "buyer", will add buyer behavior, otherwise will be "seller" (may change type to boolean in future).
*** ''npc:'' (SpeakerNPC) The NPC to add the behavior to.
*** ''prices:'' (Map<String, Integer> or LuaTable) List of items & their prices.
*** ''addOffer:'' (boolean) If <code>true</code>, will add default replies for "offer".
 
Example of adding seller behavior to an NPC:
<pre>
if game:setZone("0_semos_city") then
local frank = npcHelperentities.createSpeakerNPC("Frank")
npcHelpermerchants:addSeller(frank, merchants.shops:get("shopname"), true)
 
game:add(frank)
Line 190 ⟶ 479:
Then add the seller behavior using the custom list:
<pre>
npcHelpermerchants:addSeller(frank, priceList, true)
</pre>
 
== System Properties ==
 
Java's system properties are exposed to Lua with the <code>properties</code> object.
 
Examples:
<pre>
-- property state
if properties:enabled("stendhal.testserver") then
print("Test server enabled")
if properties:equals("stendhal.testserver", "junk") then
print("Junk enabled")
else
print("Junk disabled")
end
else
print("Test server disabled")
end
 
-- property value
local prop = properties:getValue("stendhal.testserver")
if prop ~= nil then
print("Test server enabled")
if prop == "junk" then
print("Junk enabled")
else
print("Junk disabled")
end
else
print("Test server disabled")
end
</pre>
 
== Misc ==
 
=== Typecasting ===
 
Lua does not support typecasting (as far as I know), but if the class you want to cast to has a copy constructor, achieving the same functionality is quite simple.
 
<pre>
-- "entities:getItem" returns an instance of Item
local bestiary = entities:getItem("bestiary")
 
-- in order to use the bestiary's "setOwner" method, we must convert it to an "OwnedItem" instance by calling its copy constructor
bestiary = luajava.newInstance("games.stendhal.server.entity.item.OwnedItem", bestiary)
bestiary:setOwner("Ted")
</pre>
 
= See Also =
 
* [[StendhalScripting/LuaAPI|Lua API]]
 
 
[[Category:Stendhal]]
[[Category:Documentation]]
[[Category:API]]
[[Category:Scripting]]
[[Category:Lua]]
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