Wait-for-decorator NPM

wait-for-decorator

Decorate a class method to return and wait on a Promise on the class instance before executing

Made with ❤ at @outlandish

Install

npm install wait-for-decorator --save

Usage

Wait on a single Promise:

@waitFor('promiseName')

Wait on multiple Promises (array):

@waitFor(['promiseName1', 'promiseName2'])

Wait on multiple Promises (arguments):

@waitFor('promiseName1', 'promiseName2')

Requirements

Node >=4.1.1
Babel >=5
babel-plugin-transform-decorators-legacy (Babel 6 only) (npm)

@waitFor

If you have a class that performs some asynchronous operation during initialisation but don't want consumption of its methods to be hindered by forcing their invocation to happen after initialisation is complete, you will do something like this:

class Example {
  constructor () {
      this.promise = initialise()
  }
  someMethod () {
      // Ensure init is complete internally...
      return this.promise.then(() => {
          // ...and now actually do the 'someMethod' operation
      })
  }
  anotherMethod () {
      return this.promise.then(() => {
          // Do 'anotherMethod' operation
      })
  }
}

Which gets ugly when you have lots of methods implementing this same behaviour. Instead, decorate the method using wait-for-decorator:

@waitFor('promise')
someMethod () {
    // Everything here will run after `this.promise` resolves
}

@waitFor('promise')
anotherMethod () {
    // And everything here too!
}

Examples

Wait for single Promise

class Say {
  constructor (message) {
    this.message = ''
    this.timeoutPromise = new Promise((resolve, reject) => {
      setTimeout(() => {
        this.message = message
        resolve()
      }, 50)
    })
  }

  @waitFor('timeoutPromise')
  sayMessage () {
    console.log(this.message)
  }
}

const inst = new Say('Hello, World!')
inst.sayMessage() //=> 'Hello, World!'

Wait for multiple Promises

class Say {
  constructor (messages) {
    this.message = ''
    this.firstPromise = new Promise((resolve) => {
      setTimeout(() => {
        this.message += messages[0]
        resolve()
      }, 50)
    })
    this.secondPromise = new Promise((resolve) => {
      setTimeout(() => {
        this.message += messages[1]
        resolve()
      }, 100)
    })
  }

  @waitFor(['firstPromise', 'secondPromise'])
  sayMessage () {
    console.log(this.message)
  }
}

const inst = new Say(['Hello, ', 'World!'])
inst.sayMessage() //=> 'Hello, World!'