after-ready

TC39 decorators for making classes to support one-time ready event callback handlers.

If using after-ready, a babel plugin @babel/plugin-proposal-decorators (^7.3.0) should be configured with legacy: false if the tc39 decorators are not supported natively.

Install

$ npm i after-ready

Usage

import {
  setup,
  awaitReady,
  whenReady,
  SET_READY,
  SET_ERROR,
  RESET_READY
} from 'after-ready'

@setup
class Foo {
  constructor () {
    this.init()
  }

  // `doSomething` will not resolve before `this[SET_READY]()`
  @awaitReady
  doSomething () {
    return 1
  }

  init () {
    setTimeout(() => {
      this[SET_READY]()
    }, 500)
  }
}

const result = await new Foo().doSomething()
console.log(result) // 1

@setup

@setup(onReady)

• onReady Function(err, ...args) The function to be called when the instance of the class is set as ready or errored.

Setup the class. A class must be setup with the @setup decorator then use the @awaitReady or @whenReady

After the class is @setupd, THREE methods are added to the prototype of the class.

[SET_READY](...args)

Set the class instance as ready.

If onReady function is set, it will be invoked as onReady.call(this, null, ...args).

And the methods which applied with @awaitReady and have been called before ready will resume to execute.

[SET_ERROR](error)

Set the class instance as error encountered.

If onReady function is set, it will be invoked as onReady.call(this, error).

And the methods which applied with @awaitReady and have been called before ready will be rejected.

[RESET_READY]()

Reset the ready status, or reset the error status.

@awaitReady

The method which applied this decorator will always returns a Promise.

If this[SET_READY]() has been invoked, the original method will be executed immediately.

If this[SET_ERROR](error) has been invoked, then the method will returns Promise.reject(error)

Otherwise, the original method will be paused, waiting for this[SET_READY]() or this[SET_ERROR](error) to be called.

@setup
class Foo {
  constructor () {
    this.init()
  }

  // `doSomething` will not resolve before `this[SET_READY]()`
  @awaitReady
  doSomething () {
    return 1
  }

  init () {
    setTimeout(() => {
      this[SET_ERROR](new Error('Boooooom!!'))
    }, 500)
  }
}

new Foo().doSomething().then(n => {
  console.log('the result is', n, 'but it will never reach here')
}).catch(err => {
  console.log(err.message, 'it will log "Boooooom!!"')
})

@whenReady

If no this[SET_READY]() or this[SET_ERROR](error) has been called, the original method will never be invoked.

License

MIT