How to await in constructor?

Question

I try to use await in class constructor but failed, here are my trys:

export class TheHistory {
  constructor(private readonly db: EntityManager){
        //try1: too many levels !!! try use await
        mydb.insert(god).then(() => {
          mydb.insert(human).then(() => {
            mydb.insert(city).then(() => {
              //.....
            })
          })
        })

        //try2: ERROR -- 'await'expressions are only allowed within async functions and at the top levels of modules
        await mydb.insert(god)
        await mydb.insert(human)
        await mydb.insert(city)
  }
}

Create a new async method, move your code to that, and then call that method from your constructor. — Andy, Aug 10 '21 at 03:53
https://stackoverflow.com/a/50885340/9418800 I think this is what you need — moshfiqrony, Aug 10 '21 at 04:00
You shouldn't do anything asynchronous in your constructor, because you can't handle errors. — Evert, Aug 10 '21 at 04:39

score 1 · Answer 1 · answered Aug 10 '21 at 03:59

1

You can only use await inside an async function, so either extract the code to an async method or use a immediately-invoked async function expression.

constructor(private readonly db: EntityManager){
    (async()=>{
        await mydb.insert(god)
        await mydb.insert(human)
        await mydb.insert(city)
    })();
}

answered Aug 10 '21 at 03:59

Unmitigated

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One thing to note, if anything in the constructor relies upon data returned by an `async` call, that code must also be inside the immediately-invoked function expression (IIFE). Attempting to pass a value outside the IIFE will return a promise, continuing the initial problem. – Zarepheth May 08 '23 at 15:05

score -1 · Answer 2 · answered Aug 10 '21 at 03:56

-1

Try call to constructor from outside

async function foo () {
    var myObj = await mydb.insert(god);
}

answered Aug 10 '21 at 03:56

Dilan Fernando

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How to await in constructor?

2 Answers2