generic-repo

Generic Repository for objects, based on knex.

Install

$ npm i --save generic-repo

Usage

A persistable Class

A Class can be persisted if it satisfies the following criteria:

• 1st argument of it's constructor accepts an Object that contains at least all the persistable properties.
• It has a props property that contains all the props that should be persisted.

Property serialisation

Complex property values

If a prop is of type Object it will be converted into a JSON before inserting into the database. You should handle this case appropriately in your Class constructor (see children prop of User below).

Non-complex prop values

Non-complex values such as Number, String, Boolean are send to the database as-is.

class User {
  constructor(data) {
    this.props = {  
      id_user: data.id_user,
      name: data.name,
      // Some DB's might not support a JSON datatype.
      // Therefore we might also need to *parse* back the result.
      children: data.children
        ? typeof data.children === 'string'
          ? JSON.parse(data.children)
          : data.children
        : []
    }

    // Anything outside `props` will *not* be persisted
    // - e.g `age` property will not be persisted
    this.age = 15
  }

  getName() {
    return this.name
  }
}

A usage example using the above User Class:

const GenericRepo = require('generic-repo')
const knex = require('knex')({
  client: 'sqlite3',
  connection: { filename: './test_db.sqlite' }
})

const genericRepo = new GenericRepo({
  tableName: 'user',
  primaryKey: 'id_user',
  constructAs: data => new User(data)
})

genericRepo.upsert(knex, new User({
    id_user: 'lxkkfv',
    name: 'John Doe'
  }))
  .then(() => {
    return genericRepo.get(knex, { id_user: 'lxkkfv' })
  })
  .then(user => {
    console.log(user.getName()) // 'John Doe'
  })

Ensure that your DB already has the table/columns you declared when you instantiated the repo.

API

upsert(knex, instance)

• Inserts the instance if it does not exist by primary key.
• Updates the instance if it already exists by primary key.

genericRepo.upsert(knex, user).then(() => {
  console.log(result) // [1]
})

getAll(knex, filter)

• If no filter is provided it returns all saved instances.
• If a filter is provided it returns just the matched instances.

genericRepo.getAll(knex, { name: 'John Doe' }).then(users => {
  console.log(users[0].getName()) // logs 'John Doe'
})

get(knex, filter)

• Returns an instance that matches the filter.
• Returns undefined if no instance is found.

genericRepo.getAll(knex, { name: 'John Doe' }).then(user => {
  console.log(result) // logs the 'John Doe' instance
})

exists(knex, filter)

• Returns true if a result is found, false otherwise.

genericRepo.exists(knex, { name: 'John Doe' }).then(result => {
  console.log(result) // logs `true`
})

del(knex, filter)

• Removes/Deletes the instance that matches the filter.
• Does nothing if no instance is found (no-op).

genericRepo.del(knex, { name: 'John Doe' }).then(() => {
  // Instance with name 'John Doe' was removed from the DB
})

Extend this repository

This module exports an ES6 Class which you can simply extend.

const GenericRepo = require('generic-repo')

class MySuperWowRepo extends GenericRepo {
  constructor() {
    super({
      tableName: 'employees',
      primaryKey: 'id_employee',
      constructAs: data => new Employee(data)
    })
  }

  getAllJohnDoes(knex) {
    return knex(this.tableName)
      .where({ name: 'John Doe' })
  }
}

Test

$ npm test

Authors

• Nicholas Kyriakides, @nicholaswmin

License

MIT