Loop-free way to convert List<SObject> to List<Id> with preserved order

Question

The title says it all. I insert a List into the database and want to pass a list of its Ids in the same order as in the original list. As this test proved using the Map and List constructors does not do the job.

Is there a one-liner so that I don't have to loop over a list?

List<SObject> sobjectList = new List<SObject>();
sobjectList.addAll(SmartFactory.createSObjectList('Contact', false, 2));
sobjectList.addAll(SmartFactory.createSObjectList('Account', false, 2));
sobjectList.addAll(SmartFactory.createSObjectList('Opportunity', false, 2));
insert sobjectList;

List<Id> idList = new List<Id>(new Map<Id, SObject>(sobjectList).keySet());

for(Integer i=0; i<sobjectList.size(); i++) {
    Id expectedId = sobjectList.get(i).Id;
    Id actualId = idList.get(i);
    System.assertEquals(expectedId, actualId);   
}

Note: When I say preserved order I DO NOT mean alphabetical order or anything like that. I mean it in that way that if SObject S1 is the first in the List, its Id also needs to be the first element in the id list.

Answer 1

Here goes the WTF...

In theory it has no loops (apart from the display loop). In reality I won't be surprised if it fails with "regex too complex" error on bigger dataset.

There should be a nicer way with Pattern, Matcher and negative look-behind but I'm too sober for this today...

String text;
List<Account> accs = new List<Account> {
    new Account(Name = 'Acc 1'), 
    new Account(Name = 'Acc 2'), 
    new Account(Name = 'Acc 3')
};

//  text = JSON.serialize(Database.insert(accs));
// if you don't want to insert, just pretend the next line is the result
text = '[{"id":"001A000000zBF1UIAW","success":true,"errors":[]},{"id":"001A000000zBF1VIAW","success":true,"errors":[]},{"id":"001A000000zBF1WIAW","success":true,"errors":[]}]';

---

text = text.replaceAll('"id":|"success":true|"errors":|\\[|\\]|\\{|\\}|\\"', '').replaceAll(',+', ',').removeEnd(',');
List<String> ids = text.split(',');

if(ids.size() != accs.size()){
    System.debug('Probably save has failed?');
} else {
    for(String s : ids){
        System.debug(s);
    }
}

I suspect it'll fail horribly when Database.insert(list, false) is used and one of rows fails. Up to you what you want in such scenario, null probably?

Answer 2

When you insert a list of sObjects all in one batch they will usually be assigned Ids sequentially. I don't think that this is guaranteed but in a testmethod where nothing else is happening concurrently I would expect it to always be the case.

In tried some quick tests with lists of various lengths and I wasn't able to get the records to insert out of order.

List<SObject> sobjectList = SmartFactory.createSObjectList('Contact', false, 5);
insert sobjectList;

List<Id> idList = new List<Id>(new Map<Id, SObject>(sobjectList).keySet());
idList.sort();

for(Integer i=0; i<sobjectList.size(); i++) {
    Id expectedId = sobjectList.get(i).Id;
    Id actualId = idList.get(i);
    System.assertEquals(expectedId, actualId);  
}