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I'm working on a project of mine and I have encountered a problem. Let's suppose that we have three classes (models) respectively Person, Shop, Transaction: the first and second one (Person and shop) are both interacting by creating and pushing in arrays an instance of Transaction. They all look as follows :

Person
{
  firstName:String,
  lastName:String,
  transactions:[ref:Transaction],
  ...other properties...
}

Shop
{
  name:String,
  customers:[ref:Person]
  transactions:[ref:Transaction],
  ...other properties...}
}

Transaction
{
  from:ref,//id of person||shop
  to:ref, //id of person||shop
  amount:float
  ...other properties...
}

Now when some one opens and ask the app for the balance (money they have) he/she should see a list of transaction and the name of the either of the two other class... so normal populate or lookup won't do cause in the two different collection the id's might be the same so one of the way I wanted to address it was by creating an extra id that would be used when creating any of the Person and Shop instance thus any will have its own id (example: person.id-> 1,shop.id->2). But we would do first a query on id in the Person collection and then if this result is null we would then perform the second query on id in the Shop collection... I don't really like this solution so if anyone reading this have a solution please share it with me ... Thanks in advance Edit: The Person instances may also send transactions to one an other

Chris Golden
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  • Use the built-in `ObjectId`, which (almost absolutely) guaranty uniqueness across collections. see [here](https://stackoverflow.com/questions/4677237/possibility-of-duplicate-mongo-objectids-being-generated-in-two-different-colle) – ISAE Jun 07 '21 at 22:07
  • Why exactly "normal populate or lookup won't do"? – Alex Blex Jun 08 '21 at 01:42
  • If you need to differentiate between person and shop in the transaction, why not store that like `from:{type:"person",ref:<_id>}`. Then there is no ambiguity. – Joe Jun 08 '21 at 22:09
  • the actual problem is that from might either be a shop or a person same for to – Chris Golden Jun 08 '21 at 22:49

0 Answers0