OnElementDataChange: Difference between revisions

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{{Server event}}
__NOTOC__  
__NOTOC__  
{{Server event}}
This event is triggered ''after'' an element's [[element data|data]] entry is changed. Such changes can be made on the client or the server using [[setElementData]].
This event is triggered when an elementdata entry for an element changes. A client can perform this change on the element or it can be done using [[setElementData]].
 
{{Note|These predefined variables are special in this event:
*'''client''': The [[event system#Event client|client]] global variable is set to the client that called [[setElementData]], or '''nil''' if it was called on the server.
*'''sourceResource''': The [[resource]] which changed the element data - '''nil''', if client synced data, '''resource''' element otherwise.}}


==Parameters==
==Parameters==
<syntaxhighlight lang="lua">
<syntaxhighlight lang="lua">
string theName, var theOldValue
string theKey, var oldValue, var newValue
</syntaxhighlight>  
</syntaxhighlight>  


*'''theName''': The name of the element data entry that changed
*'''theKey''': The name of the element data entry that has changed.
*'''theOldValue''': The old value of this entry before it changed. The new value can be accessed using [[getElementData]] ( source, theName ).
*'''oldValue''': The old value of this entry before it changed. See [[element data]] for a list of possible datatypes.
*'''newValue''': the new value of this entry after it changed. This will be equivalent to [[getElementData]](source, theKey).
 
==Cancelling==
This event cannot be cancelled using [[cancelEvent]]. To reverse the effect, use [[setElementData]] with the old value. See Example.


==Source==
==Source==
The [[event system#Event source|source]] of this event is the [[element]] whose elementdata changed.
The source of this event is the [[element]] whose element data changed.


==Example==  
==Example==  
<section name="Server" class="server" show="true">
<section name="Server" class="server" show="true">
<!-- Explain what the example is in a single sentance -->
This example outputs a message to players when any of their element data values is changed.
This example outputs a message to players when any of their element data values is changed.
<!-- Add the code below, an emphasis should be on making it clear, not optimized. You could provide two versions if you wish, one clear and well commented, the other optimized -->
<syntaxhighlight lang="lua">
<syntaxhighlight lang="lua">
function outputChange(dataName,oldValue)
function outputChange(theKey, oldValue, newValue)
if getElementType(source) == "player" then -- check if the element is a player
    if (getElementType(source) == "player") then -- check if the element is a player
local newValue = getElementData(source,dataName) -- find the new value
        outputChatBox("Your element data '" .. tostring(theKey) .. "' has changed from '" .. tostring(oldValue) .. "' to '" .. tostring(newValue) .. "'", source) -- output the change for the affected player
outputChatBox("Your element data '"..tostring(dataName).."' has changed from '"..tostring(oldValue).."' to '"..tostring(newValue).."'",source) -- output the change for the affected player
    end
end
end
addEventHandler("onElementDataChange", root, outputChange)
</syntaxhighlight>
</section>
<section name="Server" class="server" show="true">
This example checks and possibly reverses an element's data change.
<syntaxhighlight lang="lua">
function checkChange(theKey, oldValue)
    -- The client can only set 'special_thing' on its own player
    if (theKey== "special_thing") and (client ~= source) then
        outputChatBox("Illegal setting of " .. tostring(theKey) .. "' by '" .. tostring(getPlayerName(client)))
        setElementData(source, theKey, oldValue) -- Set back the original value
    end
end
end
addEventHandler("onElementDataChange",getRootElement(),outputChange)
addEventHandler("onElementDataChange", root, checkChange)
</syntaxhighlight>
</syntaxhighlight>
</section>
</section>
[[Category:Needs Example]]


{{See also/Server event|Element events}}
{{See also/Server event|Element events}}

Latest revision as of 15:11, 1 June 2025

This event is triggered after an element's data entry is changed. Such changes can be made on the client or the server using setElementData.

[[{{{image}}}|link=|]] Note: These predefined variables are special in this event:
  • client: The client global variable is set to the client that called setElementData, or nil if it was called on the server.
  • sourceResource: The resource which changed the element data - nil, if client synced data, resource element otherwise.

Parameters

string theKey, var oldValue, var newValue
  • theKey: The name of the element data entry that has changed.
  • oldValue: The old value of this entry before it changed. See element data for a list of possible datatypes.
  • newValue: the new value of this entry after it changed. This will be equivalent to getElementData(source, theKey).

Cancelling

This event cannot be cancelled using cancelEvent. To reverse the effect, use setElementData with the old value. See Example.

Source

The source of this event is the element whose element data changed.

Example

Click to collapse [-]
Server

This example outputs a message to players when any of their element data values is changed. 

function outputChange(theKey, oldValue, newValue)
    if (getElementType(source) == "player") then -- check if the element is a player
        outputChatBox("Your element data '" .. tostring(theKey) .. "' has changed from '" .. tostring(oldValue) .. "' to '" .. tostring(newValue) .. "'", source) -- output the change for the affected player
    end
end
addEventHandler("onElementDataChange", root, outputChange)
Click to collapse [-]
Server

This example checks and possibly reverses an element's data change. 

function checkChange(theKey, oldValue)
    -- The client can only set 'special_thing' on its own player
    if (theKey== "special_thing") and (client ~= source) then
        outputChatBox("Illegal setting of " .. tostring(theKey) .. "' by '" .. tostring(getPlayerName(client)))
        setElementData(source, theKey, oldValue) -- Set back the original value
    end
end
addEventHandler("onElementDataChange", root, checkChange)

See Also

Element events


Event functions


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