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  • License Apache-2.0

State Switch is a Change Monitor/Guarder for Async Actions.

Package Exports

  • state-switch

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (state-switch) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

STATE-SWITCH

State Switch is a Monitor/Guard for Managing Your Async Operations.

Build Status npm version TypeScript definitions on DefinitelyTyped

[State Switch Logo

EXAMPLE

Talk is cheap, show me the code!

Code

import { StateSwitch } from '../src/state-switch'

function doSlowConnect() {
  console.log('> doSlowConnect() started')
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      console.log('> doSlowConnect() done')
      resolve()
    }, 1000)
  })
}

function doSlowDisconnect() {
  console.log('> doSlowDisconnect() started')
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      console.log('> doSlowDisconnect() done')
      resolve()
    }, 1000)
  })
}

class MyConnection {
  private state = new StateSwitch('MyConnection')

  constructor() {
    /* */
  }

  public connect() {
    /**
     * This is the only 1 Right State
     */
    if (this.state.off() === true) {
      this.state.on('pending')

      doSlowConnect().then(() => {
        this.state.on(true)
        console.log(`> I'm now opened`)
      })

      console.log(`> I'm opening`)
      return
    }

    /**
     * These are the other 3 Error States
     */
    if (this.state.off() === 'pending') {
      console.error(`> I'm closing, please wait`)
    } else if (this.state.on() === true) {
      console.error(`> I'm already open. no need to connect again`)
    } else if (this.state.on() === 'pending') {
      console.error(`> I'm opening, please wait`)
    }
  }

  public disconnect() {
    /**
     * This is the only one Right State
     */
    if (this.state.on() === true) {
      this.state.off('pending')

      doSlowDisconnect().then(() => {
        this.state.off(true)
        console.log(`> I'm closed.`)
      })

      console.log(`> I'm closing`)
      return
    }

    /**
     * These are the other 3 Error States
     */
    if (this.state.on() === 'pending') {
      console.error(`> I'm opening, please wait`)
    } else if (this.state.off() === true) {
      console.error(`> I'm already close. no need to disconnect again`)
    } else if (this.state.off() === 'pending') {
      console.error(`> I'm closing, please wait`)
    }
  }
}

const conn = new MyConnection()

console.log('CALL: conn.connect(): should start to opening')
conn.connect()

console.log('CALL: conn.connect(): should not connect again while opening')
conn.connect()

console.log('CALL: conn.disconnect(): can not disconnect while opening')
conn.disconnect()

setTimeout(() => {
  console.log('... 2 seconds later, should be already open  ...')

  console.log('CALL: conn.connect(): should not connect again if we are open')
  conn.connect()

  console.log('CALL: conn.disconnect(): should start to closing')
  conn.disconnect()

  console.log('CALL: conn.disconnect(): should not disconnect again while we are closing')
  conn.disconnect()

  console.log('CALL: conn.connect(): can not do connect while we are closing')
  conn.connect()

  setTimeout(() => {
    console.log('... 2 seconds later, should be already closed ...')

    console.log('CALL: conn.disconnect(): should not disconnect again if we are close')
    conn.disconnect()
  }, 2000)

}, 2000)

Diagram

What's the meaning of the above code?

StateSwitch helps you manage the following four states easy:

[State Switch Diagram

Run

$ npm run demo

> state-switch@0.1.3 demo /home/zixia/git/state-switch
> ts-node example/demo

CALL: conn.connect(): should start to opening
> doSlowConnect() started
> I'm opening
CALL: conn.connect(): should not connect again while opening
> I'm opening, please wait
CALL: conn.disconnect(): can not disconnect while opening
> I'm opening, please wait
> doSlowConnect() done
> I'm now opened
... 2 seconds later, should be already open  ...
CALL: conn.connect(): should not connect again if we are open
> I'm already open. no need to connect again
CALL: conn.disconnect(): should start to closing
> doSlowDisconnect() started
> I'm closing
CALL: conn.disconnect(): should not disconnect again while we are closing
> I'm closing, please wait
CALL: conn.connect(): can not do connect while we are closing
> I'm closing, please wait
> doSlowDisconnect() done
> I'm closed.
... 2 seconds later, should be already closed ...
CALL: conn.disconnect(): should not disconnect again if we are close
> I'm already close. no need to disconnect again

That's the idea: we should always be able to know the state of our async operation.

API REFERENCE

Class StateSwitch

constructor(clientName?: string)

Create a new StateSwitch instance.

private state = new StateSwitch('MyConn')

on(): boolean | 'pending'

Get the state for ON: true for ON(stable), pending for ON(in-process). false for not ON.

on(state: true | 'pending'): void

Set the state for ON: true for ON(stable), pending for ON(in-process).

off(): boolean | 'pending'

Get the state for OFF: true for OFF(stable), pending for OFF(in-process). false for not OFF.

off(state: true | 'pending'): void

Set the state for OFF: true for OFF(stable), pending for OFF(in-process).

pending(): boolean

Check if the state is pending.

true means there's some async operations we need to wait. false means no async on fly.

ready(expectedState='on', noCross=false): Promise

  1. expectedState: 'on' | 'off', default is on
  2. noCross: boolean, default is false

Wait the expected state to be ready.

If set noCross to true, then ready() will throw if you are wait a state from it's opposite site, for example: you can expect an Exception when you call ready('on', true) when the on() === 'off'.

name(): string

Get the name from the constructor.

setLog(log: Brolog | Npmlog)

Enable log by set log to a Npmlog compatible instance.

Personaly I use Brolog, which is writen by my self, the same API with Npmlog but can also run inside Browser with Angular supported.

const log = Brolog.instance()
StateSwitch.setLog(log)

CHANGELOG

v0.6 master (Jun 2018)

  1. DevOps for publishing to NPM@next for odd minor versions.

v0.4 master (Apr 2018)

BREAKING CHANGE: Change the ready() parameter to the opposite side.

  • Before: ready(state, crossWait=false)
  • AFTER: ready(state, noCross=false)

v0.3 (Apr 2018)

  1. add new method ready() to let user wait until the expected state is on(true).

v0.2 (Oct 2017)

BREAKING CHANGES: redesigned all APIs.

  1. delete all old APIs.
  2. add 4 new APIs: on() / off() / pending() / name()

v0.1.0 (May 2017)

Rename to StateSwitch because the name StateMonitor on npmjs.com is taken.

  1. Make it a solo NPM Module. (#466)

v0.0.0 (Oct 2016)

Orignal name is StateMonitor

  1. Part of the Wechaty project

AUTHOR

Huan LI zixia@zixia.net (http://linkedin.com/in/zixia)

profile for zixia at Stack Overflow, Q&A for professional and enthusiast programmers
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  • Code released under the Apache-2.0 license
  • Docs released under Creative Commons