Feathers: How to fetch associations

Yes. Have a look at the example how to fetch related items. Basically, in your hook you can access another service via hook.app.service('servicename') and call the method you need. For the hook to wait you can return a Promise (that resolves with the hook object) which conveniently is what all the service methods already do:

module.exports = function(options) {
  return function(hook) {
    return hook.app.service('otherservice').find({
      query: { name: 'David' }
    }).then(page => {
      const davids = page.data;

      hook.data.davids = davids;
      // Or you can replace all the data with
      hook.data = { davids };

      // IMPORTANT: always return the `hook` object in the end
      return hook;
    });
  };
};

@daffl Thank you very much. I figured it would be this easy, but couldn't find it in the documentation, I must have missed it.

Ok so this is a find call that I have this before hook (just if you need that info)

I am only getting 25 but there are hundreds. If I remove the limit, I only get 5 items.

What is going on and how do I get all?

module.exports = function(options) {
  return function(hook) {

    const dataSet = hook.params.query.dataSet;
    const userVector = hook.params.query.userVector;

    return hook.app.service('data').find({
      query: { dataSet: dataSet, $limit:2000 }
    }).then(page => {

      // lots of magic here

      //console.log(page.data);

      hook.result = page.data;

      return hook;
    });
  };
};

It depends on what option you set for paginate.max in the configuration. It's a safeguard so that someone can't just request millions of records remotely. In all newer adapters you can turn off pagination to get all record like this:

return hook.app.service('data').find({
      paginate: false,
      query: { dataSet: dataSet }
    }).then(data => {
      // data is an array
    });

When I do that I get 0 records. When I remove the pagination: false I get 25.

Does npm ls feathers-nedb show v2.4.1? If not you may have to update your package.json accordingly.

└── [email protected]

I just verified that paginate: false works with the following example:

const feathers = require('feathers');
const rest = require('feathers-rest');
const socketio = require('feathers-socketio');
const hooks = require('feathers-hooks');
const nedb = require('feathers-nedb');
const bodyParser = require('body-parser');
const handler = require('feathers-errors/handler');
const NeDB = require('nedb');

// A Feathers app is the same as an Express app
const app = feathers();
const db = new NeDB({
  filename: './data/messages.db',
  autoload: true
});

// Parse HTTP JSON bodies
app.use(bodyParser.json());
// Parse URL-encoded params
app.use(bodyParser.urlencoded({ extended: true }));
// Register hooks module
app.configure(hooks());
// Add REST API support
app.configure(rest());
// Configure Socket.io real-time APIs
app.configure(socketio());
// Register our memory "users" service
app.use('/todos', nedb({
  Model: db,
  paginate: {
    default: 20,
    max: 50
  }
}));
// Register a nicer error handler than the default Express one
app.use(handler());

const promises = [];

for(let i = 0; i < 700; i++) {
  promises.push(app.service('todos').create({ text: `Item #${i}`}));
}

Promise.all(promises).then(function() {
  app.service('todos').find({
    paginate: false,
    query: {}
  }).then(data => console.log(data));
});

// Start the server
app.listen(3333);

I am getting 700 items logged to the console. Did you accidentally add paginate: false into the query instead of the main parameters?

This is what I did:

'use strict';

module.exports = function(options) {
  return function(hook) {

    const dataSet = hook.params.query.dataSet;
    const userVector = hook.params.query.userVector;

    return hook.app.service('data').find({
      paginate: false,
      query: { dataSet: dataSet, $limit:2000 }
    }).then(page => {

      // lots of magic here
      console.log(page.data);

      hook.result = page.data;

      return hook;
    });
  };
};

Still get 0 results and 25 with pagination variable not there and 5 results without limit.

However, I got it working with this:

'use strict';

module.exports = function(options) {
  return function(hook) {

    const dataSet = hook.params.query.dataSet;
    const userVector = hook.params.query.userVector;

    return hook.app.service('data').find({
      paginate: false,
      query: { dataSet: dataSet }
    }).then(page => {

      // lots of magic here
      console.log(page);

      hook.result = page;

      return hook;
    });
  };
};

As you see the results are no longer in the page.data but is just in the page variable.

Lesson learned :)

Oh and thanks @daffl for your help.

On the client side it doesn't work. (the paginate: false, variable).

Only query is passed between the client and the server. I'd try and avoid letting a client request all entires (if your database has a million records it will kill both, the server and the client). If there is no way around it you have to map a special query parameter (e.g. $paginate) from params.query into params in a hook on the server:

app.service('data').before({
  find(hook) {
    if(hook.params.query && hook.params.query.$paginate) {
      hook.params.paginate = hook.params.query.$paginate === 'false' || hook.params.query.$paginate === false;
      delete hook.params.query.$paginate;
    }
  }
});

I understand the warning of not allowing pagination on the client side, however, the tool I am making is just for me to run locally. Thanks again for everything.

@daffl Hi, I'm using the code you have posted to retrieve posts a user has.

module.exports = function(options) {
  return function(hook) {
    // hook.getPosts = true;
    const id = hook.result.id;
    console.log("id");

    return hook.app.service('posts').find({
      paginate: false,
      query: { postedBy: id }
    }).then(function(posts){
      console.log("posts");
      // Set the posts on the user property
      hook.result.posts = posts.data;
      // Always return the hook object or `undefined`
      return hook;
    });
  };
};

But this causes the server to go in an infinite loop and the node app ultimately crashes.

I am using MySQL as my DB connected by sequelize.

What am I doing wrong?

Update

I had setup a similar hook for posts to populate the user field based on the postedBy field. So it seems, the user hook would trigger the post hook which in turn would trigger the original user hook and the loop continues resulting in an infinite loop and memory overflow.

Any ideas how to populate only a shallow related item, i.e, the hook would pull only the related items on only the first level.

@daffl Your idea is awesome, though the code didn't work.
I had to change hook.paginate to hook.params.paginate to make it work.
And I made a little change so you can send whatever you want there.
so you can $paginate : {value: false} to disable pagination or
$paginate: { value: {default: 100, max: 2000}} to override pagination

app.service('data').before({ find(hook) { if(hook.params.query.$paginate) { hook.params.paginate = hook.params.query.$paginate.value; delete hook.params.query.$paginate; } } });

One more thing to consider is, when pagination disabled, the data is not in res.data but res itself.

@fortunes-technology You are right. I updated my code snippet. This should work:

app.service('data').before({
  find(hook) {
    if(hook.params.query && hook.params.query.$paginate) {
      hook.params.paginate = hook.params.query.$paginate === 'false' || hook.params.query.$paginate === false;
      delete hook.params.query.$paginate;
    }
  }
});

I think if $paginate is set to false (which is the point of this hook, to disable it... ), the if is going to be false, too. Maybe

app.service('data').before({
  find(hook) {
    if(hook.params.query && hook.params.query.hasOwnProperty('$paginate')) {
      hook.params.paginate = hook.params.query.$paginate === 'false' || hook.params.query.$paginate === false;
      delete hook.params.query.$paginate;
    }
  }
});

Hi there. Could someone tell me if feathers services have findOne functionality or how to implement it? Thanks!
cc @daffl

A findOne is just a find with a $limit of 1:

app.service('myservice').find({ query: { name: 'test', $limit: 1 } })
 .then(page => page.data[0])
 .then(result => console.log('Got', result);

@daffl I asked because mongoose has findOne and I suggested that it doesn't search over all rest collection if something already found. So, I thought about findOne as something smarter then search with limit=1... That's why I asked.

I usually do this for a quick findOne:

const employee = (await context.app.service('employees').find({ query: { userId: user.id }, paginate: false }))[0];

I just made a plugin for a .findOne() method: feathers-findone

I couldn't find any example on how to add the $paginate workaround for the client. So I created a before hook that runs from the app.hooks.js file with some modifications:

module.exports = function () {
  return context => {
    if (context.params.query && hook.params.query.hasOwnProperty('$paginate')) {
      context.params.paginate = context.params.query.$paginate === 'false' || context.params.query.$paginate === false;
      delete context.params.query.$paginate;
    }
  };
};

How would you go about writing a unit or integration test for this?

The same as writing any other test for Feathers.

so if i have the following in my hook

const records = getItems(context);
records.authors = await context.app.service('users') .find({ query: { _id: { $in: records.authorIds } } }, context.params);

how do i "mock" the context.app.service in my unit test?

do i need to add it to my contextBefore object?

contextBefore = { type: 'before', params: { provider: 'socketio', user: { _id: 1 } }, data: { _id: 1, }, };

i'm using the unit-test auto generated from the feathers-plus generator.
https://generator.feathers-plus.com/get-started/#unit-test-for-a-hook

or should i be using an integration test instead?

I have gone the mocking route some time ago. I think its a very bad idea. You will eventually have to mock more and more of Feathers. There is no guarentee your mocks function as feathers do and you can get false negatives, as I did.

Instanciating a Feathers app is very fast, so use Feathers instead of mocks. That's how the appraoch the cli+ test take.

I wrote an article that refers to this. https://medium.com/feathers-plus/automatic-tests-with-feathers-plus-cli-4844721a29cf

thanks eddyy, i've seen that, great article, really helped.

i was struggling on how to add the app to my context object but working it out eventually, i think!

    const app = feathers();

    contextBefore = {
      type: 'before',
      params: { provider: 'socketio', user: { _id: 1 } },
      data: {
        _id: 1,
      },
      app,
    };

Then i had to amend the test so it used async.

it('patch test', async () => {
    contextBefore.app.use('users', {
      async find() {
        return { data: [ { expectedResultObj1 }, { expectedResultObj2 } ] };
      }
    });
    contextBefore.data = {
      _id: 1,
    };
    assert(true);

    await hookToTest()(contextBefore);

    assert.deepEqual(contextBefore.data, {
      _id: 1,
      expectedResultObject1,
      expectedResultObject2,
    });
  });

Is that the right way to do it or is there a better way?

Looks good

@fortunes-technology You are right. I updated my code snippet. This should work:

app.service('data').before({
  find(hook) {
    if(hook.params.query && hook.params.query.$paginate) {
      hook.params.paginate = hook.params.query.$paginate === 'false' || hook.params.query.$paginate === false;
      delete hook.params.query.$paginate;
    }
  }
});

can use query $limit : null to bypass too