[joropito]

First of all this tutorial assumes you have knowledge of entities classes also intermediate knowledge of Pawn.
Remember that engine & fakemeta gives you tools and you should put it together to get what you want.

I’ll try to explain how to get relations between entities in a map, specifically to get entities that trigger other entities (func_button).

Entities can be triggered from another entity using it's targetname value (the name of the entity).
For that, the source entity must have it's target value with the name of the destination entity.

The following example will try to find any light entity that can be turned on/off from a func_button.

PHP Code:

// Engine way
#include <amxmodx>
#include <amxmisc>
#include <engine>
 
#define MAX_BUTTONS 10
 
new g_buttons[MAX_BUTTONS]
 
public plugin_init()
{
       new light, button
       new info[32]
       new pos
 
       while((pos <= sizeof(g_buttons)) && (light = find_ent_by_class(light, "light")))
       {
               if(!is_valid_ent(light))
                       continue   
 
               entity_get_string(light, EV_SZ_targetname, info, charsmax(info))
 
               while((button = find_ent_by_target(button, info)))
               {
                       if(!is_valid_ent(button))
                               continue
 
                       if(!find_button(button))
                       {
                               g_buttons[pos] = button
                               pos++
                               break
                       }
               }
       }
}
 
stock find_button(needle)
{
           for(new i = 0; i < sizeof(g_buttons); i++)
           {
                       if(g_buttons[i] == needle)
                                  return 1
           }
           return 0
} 


Let’s see what it does.
This will find entities of type light and not more than sizeof(g_buttons) (actually 10)

PHP Code:

       while((pos < sizeof(g_buttons)) && (light = find_ent_by_class(light, "light"))) 


Then we must check for a valid entity (if not, continue with next entity).
If it’s a valid entity, we need to get it’s name (targetname)

PHP Code:

               if(!is_valid_ent(light))
                       continue   
 
               entity_get_string(light, EV_SZ_targetname, info, charsmax(info)) 


Now we need to find which entity has our light found as a target

PHP Code:

               while((button = find_ent_by_target(button, info))) 


Again, check for valid entity and, if it’s a valid entity, we are ready to store that entity in the array and only if it’s not already stored (at bottom of the code there's a custom stock to do this work)

PHP Code:

                       if(!is_valid_ent(button))
                               continue
 
                       if(!find_button(button))
                       {
                               g_buttons[pos] = button
                               pos++
                               break
                       } 


Now we have all (no more than 10) entities which handles lights in our array.


This tutorial could be used to find other kind of relations.
Sometimes, maps makers uses multi_manager entity as a tandem between activators and targets (for example when they need just one button to activate multiple lights or door or whatever)

You can find application of this in the following plugins

https://forums.alliedmods.net/showthread.php?t=123373
https://forums.alliedmods.net/showthread.php?t=122531
https://forums.alliedmods.net/showthread.php?t=120991

[EXteRmiNaToR]

Nice!Reading it right now!

[joropito]

I prefer to build a list of entities at plugin_init and at Ham_Use only check if it's one of the selected entities.

In the Lights Mgmt plugin you can see that I catch kvd at precache on multi_manager, store un TrieCell and then populate the array.