query to get child object data

Question

I'm pretty new to SalesForce and my question should be very simple.

I'm creating an extension for a standard controller of a custom object called Bill_Account_c. This object has a master detail field with another custom object called Bill_c.

In the constructor, I want to get the Bill__c associated to the Bill_Account__c.

Here's what I've tried in apex:

public newConstructor(ApexPages.StandardController standardController) {
    controller = standardController;
    billAccount = (Bill_Account__c)controller.getRecord();

Bill__c bill = [SELECT Id, Bill_Field1__c, Bill_Field2__c FROM Bill__c WHERE Id = :billAccount.Bill__c];

}

but I get this error:

SObject row was retrieved via SOQL without querying the requested field: Bill_Account__c.Bill__c

What am I doing wrong? Sorry if this is a silly question.

Answer 1

You would need to re-query the record, so instead of what you have you would need to do this:

public newConstructor(ApexPages.StandardController standardController) {
    controller = standardController;
    billAccount = (Bill_Account__c)controller.getRecord();

    billAccount = [ Select Bill__c Where Id = billAccount.Id ];

Bill__c bill = [SELECT Id, Bill_Field1__c, Bill_Field2__c FROM Bill__c WHERE Id = :billAccount.Bill__c];

}

I think if Bill__c is not used in your VF page, you have to physically re-query it. The other solution would be to make it a hidden field in your VF page if it doesn't need to be displayed.

EDIT - or, as Mike points out an even better solution seems to be to use controller.addFields(List<String> fieldNames) thus saving yourself a SOQL query

Answer 2

Easy fix: Since you are using a Standard Controller, you need to either include that field on the VF page somewhere (so the StandardController does the querying), or you need to query it yourself.

try this:

public newConstructor(ApexPages.StandardController standardController) {
    id billAccountId = standardController.getId();
    billAccount = [SELECT id,Bill__c
                   FROM Bill_Account__c
                   WHERE id=:billAccountId];

    Bill__c bill = [SELECT Id, Bill_Field1__c, Bill_Field2__c, Bill_Account__c.Bill__c 
                    FROM Bill__c 
                    WHERE Id = :billAccount.Bill__c];

}//END init(ApexPages.StandardController standardController)