Complete SQL before return from constructor

Question

I am using pg-promise:

class Test{
    constructor(){
        this.a = db.any('SELECT * FROM test');
    }
}

If I call test.a, it will return Promise { <pending> } }.

How do I handle this problem? I cannot use .then() to solve this problem, because I hope the value can be stored in this.a before return.

Possible duplicate of [How do I return the response from an asynchronous call?](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) — CertainPerformance, Oct 19 '18 at 03:03
@CertainPerformance this one might be a little different, because `await` cannot be used in a `constructor` — Neverever, Oct 19 '18 at 03:20
@Neverever Indeed, the response should come back before actually instantiating the object. — CertainPerformance, Oct 19 '18 at 03:22

score 0 · Answer 1 · answered Oct 19 '18 at 03:21

0

You need to have a variable, foo, that is initialized as empty, then have the promise success function set the value of foo to the asynchronous result.

answered Oct 19 '18 at 03:21

Steven McConnon

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score 0 · Answer 2 · answered Oct 19 '18 at 13:14

I cannot use .then() to solve this problem, because I hope the value can be stored in this.a before return.

This is a contradictory statement. If you need the value inside the constructor, you have to use then. Otherwise, you can use then later, like this:

var t = new Test();
t.a.then(data => {});

or

const t = new Test();
const data = await t.a;

Complete SQL before return from constructor

2 Answers2