Trigger on Contracts - Example 3

// Typically you would use Batch Apex for this or if you wanted it via a trigger, it would utilize a helper class. Nonetheless, the code may be useful. 

trigger NumberOfApprovedContracts on Contract (after delete, after insert, after update, after undelete) { // trigger context variables 
       Set<Id> toUpdateAccIds = new Set<Id>(); 
       //Set<Id> zeroAccIds = new Set<Id>(); 
    
    
        // IF CONTRACT CREATED OR UNDELETED, FOR ALL THESE CONTRACTS, IF APPROVED THEN ADD CONTRACT ACCOUNT ID TO THE SET
    
       if(Trigger.isInsert || Trigger.isUndelete) { 
              for(Contract c : Trigger.new) { 
                     if(c.RecordType_Name__c == 'Approved Contract' ) { // could use dynamic/database search instead
                           toUpdateAccIds.add(c.AccountId); 
                     }
              }
       }

        // IF CONTRACT IS UPDATED, FOR ALL THESE CONTRACTS, IF THE RECORD TYPE CHANGED AND NOW IS APPROVED, THEN ADD CONTRACT IDS TO THE LIST
       
       if(Trigger.isUpdate) {
              for(Contract c : Trigger.new) {
                     if(Trigger.oldMap.get(c.Id).RecordType_Name__c != c.RecordType_Name__c && c.RecordType_Name__c == 'Approved Contract') {
                           toUpdateAccIds.add(c.AccountId);
                     }
                     // in case of a reparent you'll need to recalculate the other account as well
                     // since we are adding them to a set of Id's dupes are ommited anyway
                     if(Trigger.oldMap.get(c.Id).AccountId != c.AccountId) { // IF ACCT ID NO LONGER = ACCT ID (REPARENT) THEN...
                           toUpdateAccIds.add(c.AccountId); 
                           toUpdateAccIds.add(Trigger.oldMap.get(c.Id).AccountId);
                           //zeroAccIds.add(Trigger.oldMap.get(c.Id).AccountId);
                     }
              }
       }
       // delete needs recalc
       if(Trigger.isDelete) {
              for(Contract c : Trigger.old) {
                     toUpdateAccIds.add(c.AccountId);
              }
       }

       List<Account> affectedAccs = [select (select id from Contracts where RecordType_Name__c = 'Approved Contract') from Account where Id IN :toUpdateAccIds];

       for(Account a : affectedAccs) {
              // for count
              a.Total_Approved_Contracts__c = a.Contracts.size();
              // for true/false
              if(a.Contracts.size()>0) {
                     a.Approved_Contracts__c = true;
              } else {
                     a.Approved_Contracts__c = false;
              }
       }

       if(affectedAccs.size()>0) {
              update affectedAccs;
       }
}