I have a MongoDB database with a collection, using a mixture of Parent and Child References.
Each document in the collection includes two properties: parentId and childIds.
The parentId property is an (ObjectId) reference to the parent document.
The childIds property is an array of (ObjectId) references to child documents.
Given the collection:
[
{
"_id": {
"$oid": "625fa5b1a8142aef1a1d034d"
},
"taskId": 1,
"taskName": "New Task 1",
"parentId": null,
"childIds": [
{
"$oid": "625fa66a409d15316aada92e"
}
],
"subtasks": []
},
{
"_id": {
"$oid": "625fa66a409d15316aada92e"
},
"taskId": 2,
"taskName": "New Task 2",
"parentId": {
"$oid": "625fa5b1a8142aef1a1d034d"
},
"childIds": [
{
"$oid": "625fc16c409d15316aada94c"
}
],
"subtasks": []
},
{
"_id": {
"$oid": "625fc16c409d15316aada94c"
},
"taskId": 3,
"taskName": "New Task 3",
"parentId": {
"$oid": "625fa66a409d15316aada92e"
},
"childIds": [],
"subtasks": []
},
{
"_id": {
"$oid": "625fc16f409d15316aada94f"
},
"taskId": 4,
"taskName": "New Task 4",
"parentId": null,
"childIds": [
{
"$oid": "625fc173409d15316aada952"
}
],
"subtasks": []
},
{
"_id": {
"$oid": "625fc173409d15316aada952"
},
"taskId": 5,
"taskName": "New Task 5",
"parentId": {
"$oid": "625fc16f409d15316aada94f"
},
"childIds": [],
"subtasks": []
}
]
My goal is to populate a recursive tree structure from that collection that can be sent to the client, so any child object will be in it’s respective parent subtasks array like:
[
{
"_id": "625fa5b1a8142aef1a1d034d",
"taskId": 1,
"taskName": "New Task 1",
// This is a parent task so parentId is null
"parentId": null,
"childIds": ["625fa66a409d15316aada92e"],
// subtasks will be the objects of the childIds,
// just 625fa66a409d15316aada92e in this case
"subtasks": [
{
"_id": "625fa66a409d15316aada92e",
"taskId": 2,
"taskName": "New Task 2",
// This is a child, but also has children,
// so both parentId and childIds are present
"parentId": "625fa5b1a8142aef1a1d034d",
"childIds": ["625fc16c409d15316aada94c"],
"subtasks": [
{
"_id": "625fc16c409d15316aada94c",
"taskId": 3,
"taskName": "New Task 3",
"parentId": "625fa66a409d15316aada92e",
"childIds": [],
"subtasks": []
}
]
}
// ... More subtasks
]
},
{
"_id": "625fc16f409d15316aada94f",
"taskId": 4,
"taskName": "New Task 4",
"parentId": null,
"childIds": ["625fc173409d15316aada952"],
"subtasks": [
{
"_id": "625fc173409d15316aada952",
"taskId": 5,
"taskName": "New Task 5",
"parentId": "625fc16f409d15316aada94f",
"childIds": [],
"subtasks": []
}
]
}
// ... More tasks
]
I’m looking through similar issues that suggest using populate or aggregate but don’t have anything concrete to start with.
I currently just have this, where result is the array of documents from the collection as is:
export class Task extends Service {
constructor(options: Partial<MongooseServiceOptions>, app: Application) {
super(options);
}
find(params: Params): any {
return super.find(params).then((result: any) => {
// Todo: Populate parent-child tree structure to send to client
return result;
});
}
}
