Saving Opportunity and related Contact from single Visualforce page

Question

I have created a visualforce page that displays both opportunity and contact fields that I want users to be able to edit and save. I am using the opporutnity standard controller and added the following extension so as to be able to override (or add to) the standard save functionality with the 'SaveBoth' method (below). I am having trouble populating the contact object with the correct related record data.

I am recieveing the following error:

"Invalid foreign key relationship: Opportunity.AccountId"

public with sharing class NewLeadControllerExtension 
{
    ApexPages.StandardController controller;
    public Opportunity oppt {get; set;}
    public Contact cont {get; set;}

    public NewLeadControllerExtension(ApexPages.StandardController controller)
    {
        this.controller = controller;
        oppt = (Opportunity)controller.getRecord();
        cont = new Contact();
        cont.Id = oppt.Account.Contact.Id;
        //cont.AccountId = oppt.AccountId;
    }
    public PageReference SaveBoth()
    {
        controller.Save();
        update cont; 
        return null;
    }
}

I also tried using the line commented out in the code above instead of the line above it

cont.AccountId = oppt.AccountId

and received an

"MISSING_ARGUMENT, Id not specified in an update call"

Any advice on how to populate the contact Id correctly?

Thanks!

I have researched everything I could find on this subject but still haven't managed to solve it. The code base I started from initially can be found at Visualforce - Display fields from multiple objects

Answer 1

From the code you have posted, I see two issues with these lines of code:

cont = new Contact();
cont.Id = oppt.Account.Contact.Id;

Firstly, you aren't supposed to use an ID field that way. (EDIT:I should have said you SHOULDN'T use an ID field that way for an edit page. It is a perfectly valid way of doing it in some situations, as pointed out below). If it is an existing contact you should query it:

cont = [select id, whatever from Contact where Id = :x];

Which brings me to the second issue. You can't go from Account down to a contact, unless you have an additional lookup relationship to Contact (though I wouldn't really recommend that). I'm not even sure what you are trying to do with that line.

Answer 2

Do you have a lookup to contact from the Account or are you using person accounts?

If the former, then your field would be called something like Contact__c at a guess and you'd want to do:

cont.Id = oppt.Account.Contact__c;

If the latter, then the field will be oppt.Account.ContactId if I remember correctly.

If you're not using either of those approaches then you need to query for a contact to use, as contacts are child records of accounts, not the other way around, meaning an account could have many contacts and not just one.