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Cesar Ramirez Vasquez005391619375684564Cesar Ramirez Vasquez005391619375684564 

Im writting a trigger after insert a line with a product, i want to deduct the quantity of that line to the existing quantity in object Product__c ?

How can i achieve that im pretty new to apex basiclly i want to execute the following sql code everytime a line is inserted:
update Producto__c set CantidadExistencia__c = Producto__c.CantidadExistencia__c - Linea__c.Cantidad__c where Linea__c.Producto__c = Producto__c.id
I tried to write and my trigger looks like this:

trigger ActualizaExistencia on Linea__c(before insert, before update){
  //get a list of all the products ID's contained in the records
  //to be updated.
    Set<Id> ids = trigger.newmap.keySet();
    List<Linea__c> inv=[select id,Cantidad__c from  Linea__c where id IN :ids];


  List<Producto__c> ProIDs = new List<Producto__c>();
  for (Linea__c Ite:trigger.new){
   ProIDs.add(Ite.Producto__c);
  }
  //now get a list of all the records for products that contain the
  //above IDs
  List<Producto__c > Pros = new List<Producto__c >([select id, CantidadExistencia__c from Producto__c
  where id in:ProIDs]);
  //now loop again for all the records being updated and then for each
  //one loop through all the products records retrieved above.
  for (Linea__c obj: trigger.new){
    //we do this for loop differently so that it has an inherent check
    //to ensure that our query above returned some records
    for (integer i = 0; i < Pros.size(); i++){
      //now we make sure the record IDs match
      if (Pros.Producto__c == pros[i].id){
        Pros[i].CantidadExistencia__c = Pros[i].CantidadExistencia__c - inv[i].Cantidad__c ;
      }
    }
  }
  //update all the products records
  update Pros;
}

Is not working, i know something are really bad like trying to do this Pros[i].CantidadExistencia__c = Pros[i].CantidadExistencia__c - inv[i].Cantidad__c ;
What can i do, Thanks in advance !
SFDC_DevloperSFDC_Devloper
Hi...

  try below code..

trigger ActualizaExistencia on Linea__c(before insert, before update){
  //get a list of all the products ID's contained in the records
  //to be updated.
    Set<Id> ids = trigger.newmap.keySet();
    List<Linea__c> inv=[select id,Cantidad__c from  Linea__c where id IN :ids];


  List<Producto__c> ProIDs = new List<Producto__c>();
  for (Linea__c Ite:trigger.new){
   ProIDs.add(Ite.Producto__c);
  }
  //now get a list of all the records for products that contain the
  //above IDs
  List<Producto__c > Pros = new List<Producto__c >([select id, CantidadExistencia__c from Producto__c
  where id in:ProIDs]);
  //now loop again for all the records being updated and then for each
  //one loop through all the products records retrieved above.
  for (Linea__c obj: trigger.new){
    //we do this for loop differently so that it has an inherent check
    //to ensure that our query above returned some records
   
      //now we make sure the record IDs match
      if (Pros[0].Producto__c == pros[0].id){
        Pros[0].CantidadExistencia__c = Pros[0].CantidadExistencia__c - inv[0].Cantidad__c ;
      }
   
  }
  //update all the products records
  update Pros;
}


Thanks,
Rockzz

Cesar Ramirez Vasquez005391619375684564Cesar Ramirez Vasquez005391619375684564
Hi thank you for your fast reply; im getting the following error:

Error: Compile Error: Incompatible element type Id for collection of SOBJECT:Producto__c at line 10 column 4
Cesar Ramirez Vasquez005391619375684564Cesar Ramirez Vasquez005391619375684564
Also remember maybe i have to update multiple lines not only 1
SFDC_DevloperSFDC_Devloper
Hi,

trigger ActualizaExistencia on Linea__c(before insert, before update){
  //get a list of all the products ID's contained in the records
  //to be updated.
    Set<Id> ids = trigger.newmap.keySet();
    List<Linea__c> inv=[select id,Cantidad__c from  Linea__c where id IN :ids];


   Set<Id> ProIDs = new Set<Id>();
for (Linea__c Ite:trigger.new){
   ProIDs.add((ID)Ite.get('Producto__c'));
  }
  //now get a list of all the records for products that contain the
  //above IDs
  List<Producto__c > Pros = new List<Producto__c >([select id, CantidadExistencia__c from Producto__c
  where id in:ProIDs]);
  //now loop again for all the records being updated and then for each
  //one loop through all the products records retrieved above.
  for (Linea__c obj: trigger.new){
    //we do this for loop differently so that it has an inherent check
    //to ensure that our query above returned some records
    for (integer i = 0; i < Pros.size(); i++){
      //now we make sure the record IDs match
      if (Pros.Producto__c == pros[i].id){
        Pros[i].CantidadExistencia__c = Pros[i].CantidadExistencia__c - inv[i].Cantidad__c ;
      }
    }
  }
  //update all the products records
  update Pros;
}


Thanks,
Rockzz
Cesar Ramirez Vasquez005391619375684564Cesar Ramirez Vasquez005391619375684564
Now i get this errror 
Error: Compile Error: Initial term of field expression must be a concrete SObject: LIST<Producto__c> at line 23 column 11
That code clearly dont work