obj2fs-hoc

Higher-Order Component that adds ability for object to be stored on FileSystem by key as a JSON file, and later retrieved as Object of correct type.

Usage

In the class that you want to enhance with this HOC

import Obj2fsHOC from 'obj2fs-hoc'

Then declare your class and at the end export as Higher-Order Component

class Account {
  // have to make publicKey optional for json2Obj HOC to work
  // (object must support a constructor with no parameters)
  constructor({ publicKey } = { publicKey: '' }) {
    this.publicKey = publicKey
    this.balance = 0
    this.stake = 0
  }

  // this method defines behavior of Account data type,
  // which will be preserved after you deserialize the object from JSON
  addBalance({ amount }) {
    this.balance += amount
  }
}

export default Obj2fsHOC(Account) // enhancing Account

Wrapping Account with Obj2fsHOC adds some methods to Account type.

setKey(key) which associates unique key with an instance of an object.

async store() which saves this object as JSON string to disk with name key. It will create the file if it does not exist.

and

async retrieve() which loads object instance of correct type from disk. If the file is not found it will throw exception.throw new Error('No such key or file name found on disk')

and

retrieveretrieveThrough() which loads object instance of correct type from disk. If the file is not found it will create a new file contents of an object initialized with default constructor and then return it. This method should never fail.

Here are examples how to use the Account object:

import Account from './account'

async () => {
	let account = new Account({ publicKey: 'some public key' }) // constructor with required parameter
	const amount = 100
	account.addBalance({ amount })

	const key = 'myAccount.json'
	account.setKey(key)

	const jsonAccount = await account.store()
	// jsonAccount will be saved to disk as JSON string

	// now let's re-created another instance of the Account object from file on disk
	const generatedAccount = await (new Account().setKey(key)).retrieve()
	// can still call the addBalance method, because the object is of the right type
	generatedAccount.addBalance({ amount })

	console.log(generatedAccount.balance) // ----> 200
}