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!'

Contributing

All pull requests and issues welcome!

If you're not sure how, check out Kent C. Dodds' great video tutorials on egghead.io!