Compile Error: Loop variable must be of type Id

Question

I am not familiar in development side.am getting loop variable must be type like that. How can I resolve above the issue please can any one help me for this issue.I mention below err line in for loop..

public class dependentcon
  {
    public string cont{get;set;}
    public string acc{get;set;}


    public dependentcon
    (ApexPages.StandardController controller)
    {

    }
    public List<SelectOption> getaccounts()
    {
            List<SelectOption> optionList = new List<SelectOption>();
            List<account> acc=[select id,name from account order by Name];

            optionList.add(new SelectOption('','- None -'));

            for (account fc :acc )
            {
            optionList.add(new SelectOption(fc.id,fc.name));
            }
            return optionList;     
        }

    public List<SelectOption> getcontacts() 
  {


    List<SelectOption> optionList = new List<SelectOption>();

        Map<Id,Account> accts = new Map<Id,Account>([select name,(select name from contacts) from account]);
            Set<Id> accountIds = accts.keySet();
        system.debug('Find the value------>'+accts);
        optionList.add(new SelectOption('','- None -'));

      for(account cn :accountIds ) //Err line
      {
       optionList.add(new SelectOption(cn.id,cn.name));
      }
      return optionList;     

      }
    }

Answer 1

Change the method getcontacts(). It will work fine.

public List<SelectOption> getcontacts()
{
    List<SelectOption> optionList = new List<SelectOption>();
    Map<Id,Account> accts = new Map<Id,Account>([select name,(select name from contacts) from account]);
    system.debug('Find the value------>'+accts);
    optionList.add(new SelectOption('','- None -'));

    for(account cn : accts.values()) //Err line
    {
        optionList.add(new SelectOption(cn.id,cn.name));
    }
    return optionList;     
}

Answer 2

You took the key set from the map (of type ID), and tried to iterate over it as if it were accounts. The error is telling you the word "account" should be "Id". It looks like you were trying to list all contacts by account, which would look more like this:

for(Account ac: accts.values()) {
    for(Contact ct: ac.Contacts) {
        optionList.add(new SelectOption(ct.Id, ct.Name));
    }
}

You really don't need the map, though, and you could have done this as a linear query on contacts sorted by account ID/name (whatever your intent is).