How to upsert multiple records with Apex controller

Question

This code is able to upsert a single record in salesforce. I want it to save multiple records by breaking the long string of dates contained in the datesFromCalendar. datesFromCalendar contains data like this [5]|DEBUG|01/13/2015,01/20/2015,01/27/2015,02/03/2015,02/10/2015,02/17/2015,02/‌​24/2015,03/03/2015,03/10/2015,03/17/2015,03/24/2015,03/31/2015,04/07/2015,04/14/2‌​015,04/21/2015,06/10/2015. Each date should be a separate record in salesforce with all the other information intact and one random unique id with each set of records. For example above mentioned dates will have same unique id(any random string generated within the controller) but each should have to be a separate record in salesforce. Below is the controller which is saving all dates as a string.

public with sharing class EventsPageController {
    public Event__c Event{ 
     get {
      if (Event == null)
        Event = new Event__c();
      return Event;
    }
    set;
  }
    public String datesFromCalendar {get; set;}
    public List<String> eachDt = new List<String>();

    public void EventsPageController() {
        Event = [SELECT Id, EventDates__c,Event_Description__c,Event_Type__c,Maximum_Attendees__c,Occurrence__c,Program_Name__c FROM Event__c WHERE Id = :ApexPages.currentPage().getParameters().get('id')];

    }

    public Event__c getEvent(){
        return Event;
    }

    public String[] eventDates(){

      list<String> EventDates = new list<String>();
      list<Event__c> eventList = [SELECT Id, EventDates__c FROM Event__c WHERE Id = :ApexPages.currentPage().getParameters().get('id')];

      for(Event__c event : eventList) {
           EventDates.add(event.EventDates__c);
      }
      return EventDates;
}

    public PageReference saveData(){
        System.debug(datesFromCalendar);            
        try {
            Event.EventDates__c = datesFromCalendar;
            upsert(Event);
        } catch(System.DMLException e) {
            ApexPages.addMessages(e);
            return null;
        }
        // After Save, navigate to the default view page:
        return (new ApexPages.StandardController(Event)).view(); 

    }
}

Answer 1

So first of all you have to do a split on the variable datesFromCalendar and you split it by comma ,

  List<Event__c> events = new List<Event__c>();
  List<String> dates = datesFromCalendar.Split(',');
  String randomId = generateRandomString(5);
  for(String date : dates){
       Datetime dt = Datetime.parse(date); //Convert the string to a date
       events.add(new Event__c(
          GeneratedId__c = randomId,
          Date__c = dt,
          Event_Description__c = Event.Event_Description__c,
          Event_Type__c = Event.Event_Type__c));
          //and so on for the rest of the data you want to keep the same. 
  }
  insert events //Then you insert or upsert events

For the random id for a set of records you can generate a random string. So it will be the same for a set of dates and once inserted into the database you will also have a Salesforce unique Id.

  public static String generateRandomString(Integer len) {
    final String chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz';
    String randStr = '';
    while (randStr.length() < len) {
       Integer idx = Math.mod(Math.abs(Crypto.getRandomInteger()), 62);
       randStr += chars.substring(idx, idx+1);
    }
    return randStr; 
  }

Here is the split method in the documentation.

Here is the parse method in the documentation.

Here is the random string generator from an answer on salesforce stack exchange.

Hope it helps, let me know if you have any questions.