FeathersJs LEFT 加入另一个表（MongoDb）

Question

I have a model for a service listings like

  price: { type: Number, required: true, min: 0, default: 0 },
  itemId: {
    type: mongooseClient.Schema.Types.ObjectId,
    ref: 'items',
    required: true,
  },

and with the after all hook I am doing a fastResolve with

joins: {
items: () => async (instance, context) => {
    if (instance && instance.itemId) {
      const item = await context.app
        .service('items')
        .get(instance.itemId);

      instance.item = item;
    }
    return context;

},

so in the end when I do a find for listings, I get the item object. And while I can easily query for fields like price (listings?price%5B%24lt%5D=5000)

How should I query for inner fields of item, like weight? (when doing a listings find)

Answer 1

  const populate = (context) => {

  const stringList = [
    'vehicleId',
    'userId',
    'locationId',
  ];

  context.params.query['$populate'] = {
    path: `${stringList.join(' ')}`,
    populate: [
      {
        path: 'modelId',
        model: 'models',
        populate: {
          path: 'makeId',
          model: 'makes',
        },
      },
      {
        path: 'userId',
        model: 'users',
      },
    ],
  };

  return context;
};

Based on previous answer managed to do a research and ended up writing the following hook as the solution, for nested populate in FeathersJs

Answer 2

you can directly pass a $populate query on the front end.

for eg: ?$populate=itemId , here "itemId" is the data model's key which is referred to items model.

If you want to populate in the backend, you can create a custom hook for that.

// src/hooks/setDefaultQuery.js

const setDefaultQuery = (fieldName, defaultValue) => (context) => {
  const { params } = context;
  const { query } = params;

  if (typeof query[fieldName] === 'undefined') context.params.query[fieldName] = defaultValue;
  return context;
};

module.exports = setDefaultQuery;

on hooks, you can use the setDefaultQuery like this

{
  before: {
    all: [authenticate('jwt')],
    find: [setDefaultQuery('$populate', "itemId")],
    get: [],
    create: [],
    update: [],
    patch: [],
    remove: [],
  },
}

For more about the querying please check the link bellow https://docs.feathersjs.com/api/databases/querying.html