CODEWITHSUNDEEP
promiseobservablees6-promise
29er
29er

Reputation: 9025

Creating Promise that returns a 'thennable'. (or use Observable)

I have a function 'open' that I want to return a promise to the calling method, so that in my close function I resolve the Promise

 open(config){
        this.closePromise = new Promise()

        return this.closePromise
    }

    close(closeArgs){
        this.closePromise.resolve(closeArgs)
        ...
    }

... so that my calling method gets a callback when my 'close' function is called like this :

myService.open(myData)
.then( closeArgs => console.log('closed'))

I am getting errors like 'Promise resolver undefined is not a function' I am looking at the docs here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/resolve but nothing seems to fit my needs. ( Im starting to wonder if I should just use an Observable in this scenario, as it may fit my situation better ).

Is this a bad scenario to be using a Promise or am I just doing it wrong ? Thanks

Upvotes: 0

Views: 250

Answers (1)

Bergi
Bergi

Reputation: 664936

A promise does not have a resolve method. You need to pass an executor callback to the new Promise constructor to gain access to the resolving function:

open(config) {
    return new Promise(resolve => {
        if (this.onClose) throw new Error("not yet closed, cannot open (again)");
        this.onClose = resolve;
    });
}

close(closeArgs) {
    if (!this.onClose) throw new Error("not yet opened, cannot close (again)")
    this.onClose(closeArgs);
    this.onClose = null;
}

Upvotes: 1

Related Questions