How To Add Subcollection To Document In Firestore? - firebase

Question

Current Code
// items is an array.
// Array [
Object {
"id": "KQJfb2RkT",
"name": "first",
},
Object {
"id": "1mvshyh9H",
"name": "second",
},
]
storeSale = async ({ items }) => {
this.salesCollection.add({
status: 1,
created_at: new Date(),
updated_at: new Date(),
});
};
When adding a document in SalesCollection, I want to add items as subcollection to this document.
I would appreciate it if you could give me any advices.
I would like to save like this.
enter image description here

Answer 1

You can use a batched write, as follows:
// Get a new write batch
let batch = db.batch();
// Set the value of parent
const parentDocRef = db.collection("parentColl").doc();
batch.set(parentDocRef, {
status: 1,
created_at: new Date(),
updated_at: new Date(),
});
//Set the value of a sub-collection doc
const parentDocId = parentDocRef.id;
const subCollectionDocRef = db.collection("parentColl").doc(parentDocId).collection("subColl").doc();
batch.set(subCollectionDocRef, {
...
});
// Commit the batch
await batch.commit();
One key point to note: Actually, from a technical perspective, a parent collection and the sub-collections of the documents in this parent collection are not at all relating to each other.
Let's take an example: Imagine a doc1 document under the col1 collection
col1/doc1/
and another one subDoc1 under the subCol1 (sub-)collection
col1/doc1/subCol1/subDoc1
These two documents (and the two immediate parent collections, i.e. col1 and subCol1) just share a part of their path but nothing else.
One side effect of this is that if you delete a document, its sub-collection(s) still exist.