return not working properly when calling non-async function from async function

Question

I am trying to do a validation where each 2 seconds, the app checks into the database for a certain value, until said value is found

let conf = false;
do {
  await this.sleep(2 * 1000);
  conf = this.checkSession(hash);
  console.log(conf);
} while (!conf);

checkSessao(hash) {
  let sql = "SELECT usuario_id FROM sessao WHERE hash='" + hash + "';";

  this.db.selectGenerico(sql).then(response => {
    if (response[0].usuario_id !== null) {
      console.log("suposed to return true");
      return true;
    }

  }).catch(ex => {
    return false;
  });

  return false;
}

the thing is, the function ALWAYS return false, even though console.log("suposed to return true"); fires. I believe its related to the fact that i am calling a non-async function inside a async function. Any ideas?

Gosha_Fighten · Accepted Answer · 2019-05-27 20:28:50Z

1

Your assumption is correct. You need to return a Promise in your checkSessao function and wait until it's resolved in your loop.

checkSessao(hash) {
  return new Promise((resolve, reject) => {
    let sql = "SELECT usuario_id FROM sessao WHERE hash='" + hash + "';";    
    this.db.selectGenerico(sql).then(response => {
      if(response[0].usuario_id !== null) {
        console.log("suposed to return true");
        resolve(true);
      } else {
        resolve(false);
      }
    }).catch(ex => {
      resolve(false);
    });
  })
}

Usage:

let conf = false;
do {
  await this.sleep(2 * 1000);
  conf = await this.checkSession(hash);
  console.log(conf);
} while (!conf);

edited May 27, 2019 at 20:28

answered May 27, 2019 at 20:23

Gosha_Fighten

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1 Comment

ghybs Over a year ago

Correct answer. Would be even clearer mentioning that async/await is syntactic sugar for Promise.

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