Problem populating a list of children related to a queried sObject

Question

I have sObject1 called sObject1__c which is a parent(master-detail) to many sObjects2 each called sObject2__c.

So in my trigger I have an empty list of sObject2 related to sObject1:

sObject1__c.sObject2s__r = ();

So then I query for sObject2 and iterate over the returned list of results assigning its values to sObject1 like this:

sObject1__c.sObject2s__r.add(sObject2__c);

The code builds however the list sObject1__c.sObject2s__r remains empty. System.debug(sObject2__c) shows me that the object holds a value. Nonetheless that object doesn't get assigned to the corresponding list in sObject1.

EDIT

Here's some code as requested:

List<Interview_Result__c> listOfTestResults = [
            SELECT
                Test_Field__c
            FROM Test_Result__c
            WHERE Test_Process__c IN : mapOfTP.keySet()
        ];
for (Test_Process__c tprocess : mapOfTP.values()) {
    for (Test_Result__c tresult : listOfTestResults) {
        if (tprocess.Id == tresult.Test_Process__c) {
            tprocess.Test_Results__r.add(tresult);
        }
    }
}

Please note that the tprocess.Test_Results__r is empty before I start adding to it.

Answer 1

I don't believe this construction is valid as child relationships can't be dynamically added to sobjects unless the original query included the child sObject

For example:

Account[] aList = [select id, name from Account limit 1];
for (Account a: aList) {
    a.contacts.add(new Contact (firstname = 'foo', lastname = 'bar', email= 'foo@bar.com', accountId = a.id));
    system.debug(logginglevel.INFO,a.name + ' has contacts: ' + a.contacts);
}

displays:

someAcctName has contacts: ()

You can populate via Apex parent relationships as in the following:

Contact c = new Contact(firstname = 'foo', lastname = 'bar', email ='foo@bar.com',
                                           account = new Account (name = 'someacctname'));
system.debug(logginglevel.INFO,'contact account name='+c.account.name);