Falcor-saddle NPM

falcor-saddle

Experimental model route generation for Netflix Falcor – giddyup!

Overview

Netflix Falcor is a library for efficiently querying data across a network. It presents some useful solutions for querying data from multiple datasources, caching, and batching queries for greater performance. Yet, getting Falcor wired up to a back-end model can take a lot of repetitive code.

falcor-saddle is a module that will generate CRUD-like routes for you if you give it a set of methods for accessing your model.

Instead of writing this:

import Todo from 'model-todo';

const routes = {
  {
    route: "todos.length",
    get: (pathSet) => {
      /* repetitive implementation */
    }
  },
  {
    route: "todos[ranges]",
    get: (pathSet) => {
      /* more repetitive implementation */
    }
  },
  {
    route: "todosById[keys]",
    get: (pathSet) => {
      /* yet more repetitive implementation */
    }
  },
  /* plus routes to set, create, and delete todos... */
}

You can write this instead:

import Todo from 'model-todo';
import { createRoutes } from 'falcor-saddle';

const routes = createRoutes({
  routeBasename: 'todos',
  acceptedKeys: ['id', 'createdAt', 'content'],
  getLength: async () => Todo.count().execute(),
  getRange: async (from, to) =>
    Todo.orderBy('key').slice(from, to + 1).run(),
  getById: async (id) => Todo.get(id).run(),
  update: async (oldObj, newObj) => oldObj.merge(newObj).save(),
  create: async (params) => (new Todo(params)).save(),
  delete: async (id) => Todo.get(id).delete()
}),

...and falcor-saddle will create the following routes:

todos.length: get()
todos[ranges]: get()
todosById[keys]: get(), set()
todos.create: call()
todosById[keys].delete: call()

Usage

The usual means of using falcor-saddle is through its createRoutes() method and pass these routes to falcor-router in a manner similar to this:

import FalcorRouter from 'falcor-router';
const routes = createRoutes({ /* options */ });
const MyRouter = FalcorRouter.createClass(routes);

...and then wire that router up to Express:

/* ... other express imports */
import bodyParser from 'body-parser';
import falcorExpress from 'falcor-express';

const app = express();

app.use('/model.json', bodyParser.urlencoded({extended: false}),
  falcorExpress.dataSourceRoute( (req, res, next) =>
    new MyRouter(req, res, next)
));

/* ... additional app configuration, call to app.listen() ... */

createRoutes

Syntax

createRoutes(options)

Params

options is an object with the following key parameters:

routeBasename: String, given a value like foo it will create routes like foo.length, foo[range], fooById[keys], foo.create and foo.delete
acceptedKeys: Array of Strings, the keys you'd like your model to expose. A value of ['id', 'date', 'content'] will provide access to the id, date, and content keys from a model object. Make sure your model actually returns those keys ;)
getLength: Function or Promise of the form () => length. Must return the number of objects provided by your model.
getRange: Function or Promise of the form (from, to) => [modelObject, ...] where from and to are inclusive (i.e. (from=0, to=0) would return an Array containing the model object at interval 0).
getById: Function or Promise of the form (id) => modelObject where id is the key used to retrieve a single item from your model collection.
update: Function or Promise of the form (oldObj, newParams) => newObj where oldObj will be given as a model instance retrieved by your getById function and newParams will be a plain Object containing the key values to update. As a side-effect, you must save newObj to your model store.
create: Function or Promise of the form (newParams) => newObj where newParams will be a plain Object containing the key values used to create the new model instance. As a side-effect, you must save newObj to your model store.
delete: Function or Promise of the form (id) => null where id is the key used to retrieve a single item from your model collection. As a side-effect, you must delete the model instance with this id from your model collection.
modelIdKey: (optional) String. The primary key used by your model collection. Default: 'id'.
modelKeyGetter: (optional) Function of the form (model, key) => model[key]. It's the method used by falcor-saddle to retrieve keys from your model objects outside of the methods you specify. Rarely used.
modelIdGetter: (optional) Function of the form (model) => model['id']. It's the method used by falcor-saddle to retrieve the primary key value from your model collection. Default: (model) => modelKeyGetter(model, modelIdKey). Rarely used.

Client Usage

Given a NodeJS server providing routes created by falcor-saddle at http://localhost/api/model.json, how do you use this thing? Some examples are given below.

Creating the Client-side Model (HTTP):

const model = new falcor.Model({source: new HttpDataSource('/api/model.json') });

Length

model.
  getValue('todos.length')
  .then((response) => console.log(`todos.length: ${response}`));

Retrieve Range

model
  .get('todos[0..1]["id", "content"]')
  .then((response) => {
    console.log('todos[0..1]: ' + JSON.stringify(response));
  });

Set (Update) First Item

const aTodoResponse = await model.get('todos[0]["id", "content"]');
const updateTodoReq = { json: { todosById: { } } };
updateTodoReq.json.todosById[aTodoResponse.json.todos['0'].id] = {
  content: 'this is some updated content!'
};
model.
  .set(updateTodoReq)
  .then( (response) => {
    console.log('todos[0]:' + JSON.stringify(response));
  });

Get By Id

// bd8d468d-a330-4a13-b916-9ff46be54f3e is an example primary key value:
const key = 'bd8d468d-a330-4a13-b916-9ff46be54f3e';
model.
  .get(['todosById', [key]])
  .then( (response) => {
    console.log('todosById[key]:' + JSON.stringify(response));
  });

Create

model.
  call('todos.create', [
    // Values for first item to create:
    { content: 'snow day today' }
  ],
    // Fields to retrieve from created items:
    ['id', 'content', 'createdAt']
  )
  .then( (response) => {
        console.log('todos.create: ' + JSON.stringify(response));
  });

Delete

const firstItemId = await model.getValue(['meetings', 0, 'id']);
model
  .call('todosById.delete', [firstItemId])
  .then((response) => {
    console.log('todosById.delete: ', response);
  });

Caveats

Maturity

Falcor itself is currently in preview release. This module, and the capability it provides should be considered experimental.

We wrote it for developing our own applications, but heck, we're not sure if if falcor-saddle is even a good idea. We do know that it's helped us sketch out applications – so, at a minimum, consider it useful for that purpose.

Ranges

The way ranges are handled (e.g. todo[0..n]) is presently rather lazy. When a new item is created with todo.create it is added to the end of the range (i.e. todo[n+1]). When an item is deleted with todo.delete rather than rebuilding, the entire range we merely invalidate the item from the list.

This may change in the future.

Serialization

Although Falcor provides its own serialization, there are some corner cases where it fails: for example, we've observed returning a Date object causes an exception to be thrown. To avoid this, we've created a simple serializer.

Model serialization is implemented in src/serialization.js. Your model's return values are run through this serializer. At present, anything that's not a: