Package Exports

state-switch

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Readme

state-switch

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

Example

Talk is cheap, show me the code!

Code

import { StateSwitch } from '../'

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<'open', 'close'>('MyConnection', 'close')

  constructor() {
    /* */
  }

  public connect() {
    /**
     * This is the only 1 Right State
     */
    if (this.state.target() === 'close' && this.state.stable()) {
      this.state.target('open')
      this.state.current('open', false)

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

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

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

  public disconnect() {
    /**
     * This is the only one Right State
     */
    if (this.state.target() === 'open' && this.state.stable()) {
      this.state.target('close')
      this.state.current('close', false)

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

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

    /**
     * These are the other 3 Error States
     */
    if (this.state.target() === 'open' && this.state.inprocess()) {
      console.error(`> I'm opening, please wait`)
    } else if (this.state.target() === 'close' && this.state.stable()) {
      console.error(`> I'm already close. no need to disconnect again`)
    } else if (this.state.target() === 'close' && this.state.inprocess()) {
      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)

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<A, B>

constructor(clientName: string, initState: A | B)

In order to create a new StateSwitch instance, you need to define:

name of state A, ie: open
name of state B, ie: close
who is under management: clientName, ie: MyConn
the initial state, ie: 'close'

private state = new StateSwitch<'open', 'close'>('MyConn', 'close')

target(): A | B

Get target state

target(newState): A | B

Set target state to newState

current(): A | B

Get current state

current(newState: A|B, stable: boolean = true): A | B

Set current state to newState

if stable set to true, which is the default, that means there's no async operations on the fly. if stable set to false, means we are waiting some async operations.

stable(): boolean

Check if the state is stable.

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

inprocess(): boolean

Check for the opposite side of stable().

Return !stable()

client(): string

Get the client name.

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)

History

v0.1.0 (May 2017)

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

Make it a solo NPM Module. (#466)

v0.0.0 (Oct 2016)

Orignal name is StateMonitor

Part of the Wechaty project

Author

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

Copyright & License

Code released under the Apache-2.0 license
Docs released under Creative Commons