<function name="Add" parent="hook" type="libraryfunc"> <description> Registers a function (or "callback") with the <page>Hook</page> system so that it will be called automatically whenever a specific event (or "hook") occurs. </description> <realm>Shared and Menu</realm> <file line="23-L42">lua/includes/modules/hook.lua</file> <args> <arg name="eventName" type="string"> The event to hook on to. This can be any <page text="GM">GM_Hooks</page> hook, gameevent after using <page>gameevent.Listen</page>, or custom hook run with <page>hook.Call</page> or <page>hook.Run</page>. </arg> <arg name="identifier" type="any"> The unique identifier, usually a string. This can be used elsewhere in the code to replace or remove the hook. The identifier **should** be unique so that you do not accidentally override some other mods hook, unless that's what you are trying to do. The identifier can be either a <page>string</page>, or a <page>table</page>/object with an IsValid function defined such as an <page>Entity</page> or <page>Panel</page>. <page>number</page>s and <page>boolean</page>s, for example, are not allowed. If the identifier is a table/object, it will be inserted in front of the other arguments in the callback and the hook will be called as long as it's valid. However, if IsValid( identifier ) returns false when **any** eventName hook is called, the hook will be removed. </arg> <arg name="func" type="function"> The function to be called, arguments given to it depend on the identifier used. <warning> Returning any value besides nil from the hook's function will stop other hooks of the same event down the loop from being executed. Only return a value when absolutely necessary and when you know what you are doing. ⤶ It will also prevent the associated `GM:*` hook from being called on the gamemode.⤶ It WILL break other addons. </warning> </arg> </args> </function> <example> <description> This will hook onto the "Think" event with the function onThink, printing to the console whenever the event occurs. </description> <code> local function onThink() print( "onThink has been called" ) end hook.Add( "Think", "Some unique name", onThink ) </code> <output> "onThink has been called" repeating continuously. </output> </example> <example> <description>This works the same as above, but defines the function inside hook.Add rather than above it.</description> <code> hook.Add( "Think", "Another unique name", function() print( "Think has been called" ) end ) </code> <output> "Think has been called" repeating continuously. </output> </example> <example> <description> This code demonstrates how you can add a table function with a 'self' argument, without the use of a wrapper function </description> <code> local myTable = {} function myTable:IsValid() return true end function myTable:PlayerInitialSpawn(ply) print( "CustomHook", self, ply ) end hook.Add( "CustomHook" , myTable , myTable.PlayerInitialSpawn ) hook.Run( "CustomHook" ) </code> <output> "CustomHook table: 0x00000000 Player [1][PotatoMan]" </output> </example>