Help with Trigger Error Messages

Question

I am trying to get the code below to throw and error message if a picklist field (VIP_Type__c) on a custom object already exists in the Parent's (Contact) related list.

I am getting 2 errors and I don't know what they mean or how to resolve. Can anyone help?

Line 19 - Method does not exist or incorrect signature: void contains(String) from the type Set<VIP_Type__c>

Line 27 - Method does not exist or incorrect signature: void add(String) from the type Set<VIP_Type__c>

    Set<Id> acctIds = new Set<ID>();
    Set<Id> contIds = new Set<ID>();
    map<Id, set<VIP_Type__c>> contact_type_map = new map<Id, set<VIP_Type__c>>();

// Get all the Account & Contact Ids in the Set 
        for(VIP_Type__c vip : Trigger.new){
            acctIds.add(vip.Account__c);
            contIds.add(vip.Contact__c);
            contact_type_map.put(vip.Contact__c, new set<VIP_Type__c>{vip});
    }

        List<VIP_Type__c> vipRecs = [SELECT Id,Account__c,Contact__c,VIP_Type__c
                                    FROM VIP_Type__c
                                    WHERE Contact__c in:contIds AND ID NOT in:trigger.new];

//Check for VIP Types already entered for Contact
    for(VIP_Type__c objVIP: vipRecs){

        if(contact_type_map.get(objVIP.Contact__c).contains(objVIP.VIP_Type__c)){
system.debug('@@@### - Error message:  '+contact_type_map.get(objVIP.Contact__c));


                trigger.newMap.get(objVIP.VIP_Type__c).addError('This Type already exists for this Contact');

        }
        else{
            contact_type_map.get(objVIP.Contact__c).add(objVIP.VIP_Type__c);
        }
    }

Answer 1

You've got some false assumptions in your logic. If we presume that you want a unique combination of account, contact, and VIP type, you need a different map. Here's a close approximation to what you need:

Set<Id> acctIds = new Set<ID>();
Set<Id> contIds = new Set<ID>();
Map<VIP_Type__c, VIP_Type__c> contactTypeMap = new Map<VIP_Type__c, VIP_Type__c>();
// Get all the Account & Contact Ids in the Set 
for(VIP_Type__c vip : Trigger.new) {
    acctIds.add(vip.Account__c);
    contIds.add(vip.Contact__c);
    VIP_Type__c key = new VIP_Type__c(Contact__c=vip.Contact__c, Account__c=vip.Account__c, VIP_Type__c=vip.VIP_Type__c);
    if(contactTypeMap.put( key, vip ) != null) {
        contactTypeMap.get( key ).addError( 'This type already exits for this Contact' );
    }
}

List<VIP_Type__c> vipRecs = [SELECT Id,Account__c,Contact__c,VIP_Type__c
                            FROM VIP_Type__c
                            WHERE Contact__c = :contIds AND Account__c = :acctIds];
//Check for VIP Types already entered for Contact
for(VIP_Type__c vip: vipRecs) {
    VIP_Type__c key = new VIP_Type__c(Contact__c=vip.Contact__c, Account__c=vip.Account__c, VIP_Type__c=vip.VIP_Type__c);
    if(contactTypeMap.containsKey(key)) {
        contactTypeMap.get(key).addError('This Type already exists for this Contact');
    }
}

Answer 2

Methods on a collection need to be given an argument of the same type as the type contained in the collection.

You have your set declared as Set<VIP_Type__c>, a Set of VIP_Type__c SObjects. The data you're trying to pass to the contains() method is someRecord.VIP_Type__c, which is a string.

String != SObject type.

Change Set<VIP_Type__c> to Set<String>, and the errors should be resolved.

As a side note, this is a good illustration of why naming things is important¹. Having a VIP_Type__c field on your VIP_Type__c custom SObject is allowed, but it ends up making it easier to make mistakes in code.

^{1: ...and one of the 2 "hard problems" in computer science, those being: cache invalidation, naming things, ...and off-by-one errors}