如何在 Firestore 中递归搜索结果？

Question

I'm new to Node and Firebase.

I'm currently working on a crafting calculator for a game and have the game items stored in Firebase. Some items are composite items, for example:

1 Lumber Plank = 5 Logs

Based on such requirements, I've structured all the items as a single collection titled as items in Firebase.

Log would be persisted as:

{
  "type": "basic",
  "name": "log"
}

While lumber plank would be:

{
  "type": "composite",
  "name": "lumber plank",
  "materials": ["log"],
  "material_values": [5]
}

With such a structure, I'm trying to construct a crafting tree by recursively searching through the database. A final structure would look as such:

{
    "name": "board",
    "count": 1,
    "materials": [
        {
            "name": "lumber plank",
            "count": 1,
            "materials": [
                {
                    "name": "log",
                    "count": 5,
                    "materials": null
                }
            ]
        }
    ]
}

I'm having trouble with understanding the callbacks while debugging and this piece of code currently returns undefined followed by log (I'm assuming this comes from the console.log within the search function).

async function search(item, result, count) {
    let calcItem = {
        name: item,
        count: count
    };

    db.collection("items")
        .doc(item)
        .get()
        .then(doc => {
            const data = doc.data();
            if (data.type === basic) {
                calcItem.materials = null;
                result.push(calcItem);
                return result;
            } else {
                let materials = data.materials;
                let materialsCount = data.material_values;
                calcItem.materials = [];
                for (let i = 0; i < materials.length; i++) {
                    console.log(materials[i]);
                    search(materials[i], calcItem.materials, materialsCount[i]);
                }
            }
        });
}

let item = "lumber plank";

search(item, [], 1).then(result => console.log(result));

Would appreciate any pointers/tips here. Thanks

---

Following feedback from Doug,

I've kinda refactored my code based on your comments and I'm seeing some progress.

function recursiveSearch(item, count, result) {
    let calcItem = {
        name: item,
        count: count
    };

    dbSearch(item).then(function (doc) {
        const data = doc.data();
        console.log(data);

        if (data.type === basic) {
            calcItem.materials = null;
            result.push(calcItem);
            return result;
        } else {
            let materials = data.materials;
            let materialsCount = data.material_values;
            calcItem.materials = [];
            for (let i = 0; i < materials.length; i++) {
                recursiveSearch(materials[i], materialsCount[i], calcItem.materials);
            }
        }
    });
}

function dbSearch(item) {
    return Promise.resolve(db.collection("items")
        .doc(item)
        .get()
        .then());
}

Log now outputs the search correctly.

{
  material_values: [ 5 ],
  materials: [ 'log' ],
  name: 'lumber plank',
  type: 'composite'
}
{
  name: 'log',
  type: 'basic'
}

However, if I understand it correctly, if I were to add in this line it's still going to return undefined, am I right?

console.log(recursiveSearch("lumber plank", 1, [])

If so, how do I actually log out the entire item structure whilst completing all the recursive searches?

Sorry if the question sounds kinda dumb. I primarily come from a Java background and dealing with promises/async/await is entirely new to me

Answer 1

You're not dealing with promises correctly. search doesn't actually return a "real" promise, but the caller is expecting it to do so. Since it's async , but doesn't return a value directly, it's actually returning is a promise that always resolves to undefined . It's also apparently intended to be a recursive function, which is making it harder to understand (did you mean to return the promise from the inner call to search ?).

Minimally, you should start by making search return the promise chain that it establishes:

return db.collection("item")...get().then()

This will let you receive the value returned by the then callback.

I'll also point out that you're started to use async/await syntax, but never committed to using await to make this code more easy to read, which is a bit confusing.