APEX trigger lookup field value in onther custom object

Question

This is what I have:

trigger ComplaintInitialize on Complaints__c (before insert, before update)
{
  for(Complaints__c Complaint : Trigger.new)
  {

    if(Complaint.RecordType_Name__c == 'ComplaintInitialize')
    {
       Id recordTypeId = Schema.SObjectType.Complaints__c.getRecordTypeInfosByDeveloperName().get('ComplaintOffice').getRecordTypeId();
       If(String.isBlank(Complaint.Case__c) == false)
       {
          Case C = [Select Id, OwnerId, ContactId, Intermediary__c, Polisnummer_lookup__c, Account.FirstName, Account.LastName, 
                    Contact.First_Name__c, Contact.LastName, Contact.MailingStreet, Contact.MailingPostalCode, Contact.MailingCity, 
                    Contact.Gender__c, Contact.Phone, Contact.Email from Case Where Id =: Complaint.Case__c ];
          Complaint.Employee__c = C.OwnerId;
          User KB = [select Id from User where LastName = :'ComplaintOffice'];
          Complaint.OwnerID = KB.id;
          User H = [select Id, Email, Department, Division from User where Id =: C.OwnerId];
          User TL = [Select Id from User Where Department =: H.Department AND IsActive =: true AND Function__c =: 'Complaint_Handler' LIMIT 1];
          Complaint.Complaint_Handler__c = TL.Id;

so far so good

but here I got stuck:

Illegal assignment from List to Complaints__c

at line....

      Complaints__c DT = [Select Id, Date__c, FirstContactDate__c, FirstContactDateAAV__c from PeriodOfTime__c Where Date__c =: date.today() LIMIT 1];
      If(Complaint.Received_by__c == 'Complaint coordinator AAV')
          {Complaint.Deadline__c = DT.FirstContactDateAAV__c;}
      else
          {Complaint.Deadline__c = DT.FirstContactDate__c;}

What am I doing wrong in the last part? (The 'Limit 1' is not necessary because there is only 1 record in the database with date of today)

Answer 1

Since you're new to Salesforce, I'd recommend that you ditch this approach. It's highly inefficient and manual. Instead, you can use BusinessHours and Custom Metadata to provide a configurable setting for your trigger.

BusinessHours

In Setup, create a new Business Hours setting. You can just specify the start and end times as 12:00AM on each end to make your calculations easier.

Holidays

You can specify holidays for your Business Hours--this will allow you to skip days off using the BusinessHours library.

Custom Metadata

Create a Custom Metadata object with a single custom field, Value__c that specifies the number of business days to calculate.

Trigger

Now, for each record, you can simply query your Custom Metadata for each record, use the BusinessHours library to calculate the appropriate date, and then assign the result to the custom field. That code would look like:

trigger on Complaints__c (before insert) {
  BusinessHours complaintHours = [SELECT Id FROM BusinessHours WHERE Name='Complaint Deadlines'];
  for(Complaints__c record: Trigger.new) {
      Deadline__mdt[] deadline = [SELECT Value__c FROM Deadline__c WHERE Name = :record.Option__c];
      if(deadline.size() == 1) {
          record.Deadline__c = BusinessHours.add(complaintHours.Id, DateTime.newInstance(Date.today(), Time.newInstance(0,0,0,0)), 86400000).date();
      }
   }
}

This may not be exactly correct, so some changes may be necessary. The documentation should help you out here.