Send an email template from trigger on Quote Item

Question

I want to send an email template to a contact record, based upon QuoteItem field. On the QuoteItem object I have a field called update_del (checkbox). When the field is set true, I want to send an email template.

The QuoteItem is child object to the Quote object, having master-detail relationship. On the Quote object I have a field called Email__c and I want to send an email template to the address which is set in that field.

I tried the code Below, but I am getting an error when executing the SOQL Query

trigger emailtemplate2 on Quote_Item__c(after update)
{
    List<Quote_Item__c> oList = Trigger.new;
    List<Quote_Item__c> nList = trigger.old;

    if(oList[0].Updated_del__c !=nList[0].Updated_del__c) {

        Set<Id> QuoteItemIds= new Set<Id>();
        List<Quote__c> sList = [
                    select id,Email__c
                    from Quote__c
                    where Quote__r.Email__c =:nList[0].Quote__c.Id
                    limit 1
                    ];
        // Error Occuring Point
        Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();

        if(oList[0].Quote_Item__c== 'true') {
            EmailTemplate et=[Select id from EmailTemplate where name = 'quote3' limit 1];
            mail.setTemplateId(et.id);
            mail.setToAddresses(new String[] {sList[0].email});
            mail.setTargetObjectId(sList[0].id);
            mail.setSaveAsActivity(false);
            Messaging.SendEmailResult [] r = Messaging.sendEmail(
                    new Messaging.SingleEmailMessage[] {mail});  
        }
    }
}

Answer 1

There are a few issues with the trigger:

1) Trigger is not bulkified - the current code will only work when you update 1 record at a time. Have a read here and here.

2) nList[0].Quote__c.Id - Quote__c is the same as Quote__r.Id (__r and not __c, but then you won't have access to parent related fields using trigger.old - only fields on the same sObject). In order to get parent record's fields you need to run a SOQL query.

3) where Quote__r.Email__c =:nList[0].Quote__c.Id - Doesn't make any sense. You are comparing an email string to a record ID, did you mean where Quote__c = :nList[0].Quote__c ?