Knex Model Wrapper

Objective

Create a simple data models backed by knex.

• Promise API for data operations (get, insert, update, delete)
• Validate data going into the db and throw clear errors
• Provide before and after hooks
• Export plain old JavaScript objects, no magic

Usage

Model definition

First we create a ModelWrapper. This generates models based on any given default options for each model to use such as the knex instance.

See lib/index.js for full list of ModelWrapper options.

We then use the ModelWrapper to generate a model. This is given the configuration of the model such as the table name, schema to validate the incoming data as well as hooks and custom validation functions.

See lib/model.js for full list of Model constructor options.

var ModelWrapper = require("knex-model-wrapper");
var db = require("knex")();
db.connect();

// Configure the ModelWrapper to generate models
var model = new ModelWrapper({
  db: db
});

// Create models
var User = model.create({
  tableName: "users",
  schema: {
    id: {
      type: "number"
    },
    email: {
      type: "string",
      required: true
    },
    password: {
      type: "string",
      required: true
    }
  }
});

Using models

Once a model is created it can be used to perform basic functions such as getting, inserting, updating and deleting data.

The basic flow of an insert is:

1. Validate the data against the schema
2. Call any before hooks
3. Create a knex query to insert the data into the db
4. Call any after hooks
5. Return the saved object from the db

See lib/model.js for full list of functions.

User.insert({
  email: "[email protected]",
  password: "a9789zf89209df3232" // hashed password :)
})
.then(function (user) {
  console.log(user); // {id: 5, email: "[email protected]", password: "a9789zf89209df3232"}
})
.catch(function (err) {
  // do something with validation errors etc
});

User.get(5).then(function (user) {
  console.log(user); // {id: 5, email: "[email protected]", password: "a9789zf89209df3232"}
});

User.update({id: 5}, {
  email: "[email protected]"
})
.then(function (user) {
  console.log(user); // {id: 5, email: "[email protected]", password: "a9789zf89209df3232"}
});

User.count()
.then(function (data) {
  console.log(data); // {count: 1}
});

User.delete(5)
.then(function (data) {
  console.log(data); // {deleted: 1}
});

Using model hooks

Model hooks are triggered before and after an event such as insert, update, delete, insertMany, deleteMany.

Hooks be registered on a model when creating or added afterwards using the before and after function.

Model hooks should not mutate the data, they are intended to provide a means to trigger other processes such as syncing data to a search engine.

// Add a hook when creating the model
var User = model.create({
  tableName: "users",
  schema: {
    id: {
      type: "number"
    },
    email: {
      type: "string",
      required: true
    },
    password: {
      type: "string",
      required: true
    }
  },
  beforeHooks: {
    insert: [
      function myHook (attrs) {
        console.log(attrs);
      }
    ]
  }
});

// Add a hook after creating the model
User.before("insert", function (attrs) {
  console.log(attrs); // Do something with the attributes
})

Pro Tips

knex-model-wrapper uses knex which can be accessed via the db key of models for building custom queries.

knex-model-wrapper uses hannibal to validate data and perform any transforms. This is exposed on the model instance as the hannibal key. Custom validators and transforms can be registered when instantiating the model object.

Schemas schemas can be composed together easily. For example if all your models have id, createdAt and updatedAt properties a schema can be defined for those base attributes and merged into all other schemas.

var baseSchema = {
  id: {
    type: "number"
  },
  createdAt: {
    type: "date",
    default: function () {
      return new Date();
    }
  },
  updatedAt: {
    type: "date",
    transforms: "newDate"
  }
};

var User = model.create({
  schema: Object.assign(baseSchema, {
    firstName: {
      type: "string"
    }
  })
});

## Tests

A postgreSQL database is a pre-requisite for running the tests. Create a database and configure it in the knexfile. To generate a knexfile run npm run setup-tests.

To set up the test db with default settings in psql:

create database knex_model_wrapper_test;

Test are run using mocha ./node_modules/.bin/mocha or the npm test script npm test.