Cross Object Field Update Trigger - Need Help!

Question

I have what seems to be a simple cross object field update. When the Operational Status on the Parent (Account) is updated, I want the value of the Contract Status field on the Child (Master Contract) to be updated to a corresponding value.

I need to match the Parent to the Child on Acc.Long_Account_Id__c = MC.Account_Id__c (it's a one-to-one relationship)

Here is what I've come up with thus far:

trigger UpdateStatus on Account (after update) {  
 List<Master_Contract__c> mcs = new List<Master_Contract__c>();  
 Set<Master_Contract__c> mcSet = new Set<Master_Contract__c>();  
 Map<ID, Master_Contract__c> mcMap = new Map<ID,Master_Contract__c>(); 
     for (Account acc: Trigger.new)
     {
      if(acc.Operational_Status__c =='Operational') 
      {
      mcSet.add(acc.Long_Account_Id__c);
      }
     }    mcs = [Select Account_Id__c, Contract_Status__c from Master_Contract__c where Account_Id__c n :mcSet];
     for(Account acc: Trigger.new)  
      {
        for(Master_Contract__c mc:mcs)
        {
         if(acc.Long_Account_Id__c==mc.Account_ID__c && acc.Operational_Status__c =='Operational')
           mc.Contract_Status__c = 'Active';
         }
        } 
       if(mcs.size() >0)
       update mcs;  }

I am currently getting this error: Error: Compile Error: Incompatible element type String for collection of SOBJECT:Master_Contract__c at line 9 column 6

Suggestions?

Answer 1

Here is the sort of code I would write (updated after added comment):

trigger UpdateStatus on Account (after update) {
     Map<Id, String> requireds = new Map<Id, String>();
     for (Account acc: Trigger.new) {
         Account old = Trigger.oldMap.get(acc.Id);
         if (old.Operational_Status__c != acc.Operational_Status__c) {
             String s;
             if (acc.Operational_Status__c == 'Operational') {
                 s = 'Active';
             } else if (acc.Operational_Status__c == 'Cancelled') {
                 s = 'Terminated';
             } else {
                 s = 'Pending';
             }
             requireds.put(acc.Long_Account_Id__c, s);
         }
     }
     if (m.size() > 0) {
         List<Master_Contract__c> updates = new List<Master_Contract__c>();
         for (Master_Contract__c mc : [
                 Select Id, Contract_Status__c, Account_Id__c
                 from Master_Contract__c
                 where Account_Id__c in :requireds.keySet()
                 ]) {
             String required = requireds.get(mc.Account_Id__c);
             if (mc.Contract_Status__c != required) {
                 mc.Contract_Status__c = required;
             }
             updates.add(mc);
         }
         update mcs;
    }
}

The above code assumes that Long_Account_Id__c is an ID-based reference; if it is a text field make the collection data type String instead.

Answer 2

It looks as though the error is with the line
mcSet.add(acc.Long_Account_Id__c).

Your "mcSet" is a set of Master_Contract__c objects, however "acc.Long_Account_Id__c" which is of type Id, not a Master_Contract__c.

Since you don't use "mcSet" anywhere else I believe changing its type from
Set < Master_Contarct__c > to Set < Id > would fix the error you were receiving and still allow it to be used properly in the following piece of code:

mcs = [Select Account_Id__c, Contract_Status__c from Master_Contract__c where Account_Id__c IN :mcSet]