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() start connecting')
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      console.log('doSlowConnect() connected')
      resolve()
    }, 1000)
  })
}

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

class MyConnection {
  private state = new StateSwitch<'connected', 'disconnected'>('MyConnection', 'disconnected')

  constructor() {
    /* */
  }

  public connect() {
    /**
     * This is the right state
     */
    if (this.state.target() === 'disconnected' && this.state.stable()) {
      this.state.target('connected')
      this.state.current('connected', false)

      doSlowConnect().then(() => {
        this.state.current('connected', true)
        console.log(`I have just connected.`)
      })

      console.log(`I'm connecting now`)
      return
    }

    /**
     * Error state
     */
    if (this.state.target() === 'disconnected' && this.state.inprocess()) {
      console.error(`I'm disconnecting, please wait`)
    } else if (this.state.target() === 'connected' && this.state.stable()) {
      console.error(`I'm already connected. no need to connect again`)
    } else if (this.state.target() === 'connected' && this.state.inprocess()) {
      console.error(`I'm connecting, please wait`)
    }
  }

  public disconnect() {
    /**
     * This is the right state
     */
    if (this.state.target() === 'connected' && this.state.stable()) {
      this.state.target('disconnected')
      this.state.current('disconnected', false)

      doSlowDisconnect().then(() => {
        this.state.current('disconnected', true)
        console.log(`I have just disconnected.`)
      })

      console.log(`I'm disconnecting now`)
      return
    }

    /**
     * Error state
     */
    if (this.state.target() === 'connected' && this.state.inprocess()) {
      console.error(`I'm connecting, please wait`)
    } else if (this.state.target() === 'disconnected' && this.state.stable()) {
      console.error(`I'm already disconnected. no need to disconnect again`)
    } else if (this.state.target() === 'disconnected' && this.state.inprocess()) {
      console.error(`I'm disconnecting, please wait`)
    }
  }
}

const conn = new MyConnection()

console.log('CALL: conn.connect()')
conn.connect()

console.log('CALL: conn.connect()')
conn.connect()

console.log('CALL: conn.disconnect()')
conn.disconnect()

setTimeout(() => {
  console.log('CALL: conn.connect()')
  conn.connect()

  console.log('CALL: conn.disconnect()')
  conn.disconnect()

  console.log('CALL: conn.disconnect()')
  conn.disconnect()

  console.log('CALL: conn.connect()')
  conn.connect()

  setTimeout(() => {
    console.log('CALL: conn.disconnect()')
    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()
doSlowConnect() start connecting
I'm connecting now
CALL: conn.connect()
I'm connecting, please wait
CALL: conn.disconnect()
I'm connecting, please wait
doSlowConnect() connected
I have just connected.
CALL: conn.connect()
I'm already connected. no need to connect again
CALL: conn.disconnect()
doSlowDisconnect() start disconnecting
I'm disconnecting now
CALL: conn.disconnect()
I'm disconnecting, please wait
CALL: conn.connect()
I'm disconnecting, please wait
doSlowDisconnect() disconnected
I have just disconnected.
CALL: conn.disconnect()
I'm already disconnected. no need to disconnect again

That's the idea: we have to know the state of our async operation.

API Reference

Class StateSwitch<A, B>

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

Inorder 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 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