Apex Class that checks a checkbox when contact is generated (math.random)

Question

I have partly created an apex trigger that randomly selects a contact that is in a specific campaign. This works and I can cycle through the contacts at random. When i refresh the page however I am still allowed to cycle through the contacts again. I should be able to generate the contact once.

I now have a checkbox named 'Mascot_Winner__c' that is unchecked. Is there a way at all to check this checkbox when the contact has been generated at all? Does this checkbox need to be on the contacts object or does it need to be on the campaign or accounts?

Thanks for you help

Controller:

public class MascotController
{
   public List<Contact> contacts{get;set;}

   public MascotController()
   {
        getContacts();
   }
   public void getContacts()
   {
        Integer count = [SELECT COUNT() FROM Contact];
        Integer rand = Math.floor(Math.random() * count).intValue();
        Set<Id> contactIds = new Set<Id>();
        contacts = new List<Contact>();
        for(CampaignMember cm : [Select Id, ContactId from CampaignMember where Status = 'To be Called' and Campaign.Name = '2014/15 Mascot Data'])
        {
           contactIds.add(cm.ContactId);
        }
        List<String> orderBys = new List<String>{'Email Asc','Email Desc','Lastname Asc','Firstname Desc','LastModifiedDate Desc','LastModifiedDate Asc','CreatedDate Asc','CreatedDate Desc','Id Asc','Id Desc'};
        String orderBy = orderBys.get(Math.mod(rand,orderBys.size()));
        contacts = Database.query('Select Name From Contact where ID in :contactIds Order By ' + orderBy + ' Limit 1 OFFSET :rand');
    }
}

VF Page:

<apex:page showHeader="true" sideBar="true" controller="MascotController">
   <apex:form >
      <apex:pageblock id="pb" title="Mascot Winner">
         <apex:commandButton value="Generate Winner" action="{!getContacts}" rerender="randomContacts"/>
         <apex:outputPanel id="randomContacts">
          <apex:pageblock >
              <apex:PageBlockTable value="{!contacts}" var="item">
                  <apex:column headerValue="Contact Name" value="{!item.Name}"/>
              </apex:PageBlockTable> 
           </apex:pageblock>
         </apex:outputPanel>
      </apex:pageBlock>
   </apex:form>
</apex:page>

Answer 1

You can add the check box field on the Contacts. Check the checkbox once the contact has been chosen as the winner. Then, in the query, you can have a check whether the contact has already been selected as a winner or not. You have to write an update DML statement after you choose the winner contact.
Change this contacts = Database.query('Select Name From Contact where ID in :contactIds Order By ' + orderBy + ' Limit 1 OFFSET :rand'); to
contacts = Database.query('Select Name From Contact where ID in :contactIds AND checkBoxField != True Order By ' + orderBy + ' Limit 1 OFFSET :rand');

Answer 2

Assuming that your contact record can be a part of multiple campaigns, which will can lead that contact to be a winner of multiple campaigns. So, my suggestion will be to create a contact lookup on campaign and populate the winner contact's id at campaign level (in contact lookup). this will solve:-

1. Easy reporting for campaign and their winners
2. Allows contact to be a winner of multiple campaigns
3. Once winner is selected i.e. Campaign's winner contact field is populated, your code can skip re-calculation logic for winner