CODEWITHSUNDEEP
javascriptpromise
guijob
guijob

Reputation: 4488

Promise.resolve() isn't being executed

I'm trying to save a brand new object into my database but only if it doesn't exists yet. For this, I created this method in other to make two validations: (1) if object is missing and (2) if object already exists. If everything is ok, then save. Code is below:

exports.new = (obj) => {
  return Promise.resolve(() => {
    if (!obj) throw Error('object is missing');

    this.getOneAsync(obj).then(repeatedObj => {
      if (repeatedObj.length != 0) throw Error('Object already saved!');
      return obj;
    });
  }).then(obj => {
    var newObj = createModel(obj);

    return newObj.saveAsync();
  })
};

Unfortunately, Promise.resolve() aren't being executed. My code jump straight to then() clause and obj isn't what I expected, always returning { length: 0, name: '' }.

What am I doing wrong? Any help will be appreciated.

Upvotes: 0

Views: 99

Answers (2)

guijob
guijob

Reputation: 4488

After clarifications here, this way works using Promise.resolve():

exports.new = (obj) => {
  return Promise.resolve().then(() => {
    if (!obj) throw Error('object is missing');

    this.getOneAsync(obj).then(repeatedObj => {
      if (repeatedObj.length != 0) throw Error('Object already saved!');
      return obj;
    });
  }).then(obj => {
    var newObj = createModel(obj);

    return newObj.saveAsync();
  })
};

Upvotes: 0

Felix Kling
Felix Kling

Reputation: 816422

Promise.resolve() is executed, but not the function you pass to it. Promise.resolve immediately resolves the promise with the value you pass to it. It does not call the function. .then is called with the function you pass to Promise.resolve.

Promise.resolve is not useful in your case. Instead do something like

exports.new = (obj) => {
  if (!obj) return Promise.reject(new Error('object is missing'));

  return this.getOneAsync(obj)
    .then(repeatedObj => {
      if (repeatedObj.length != 0) throw Error('Object already saved!');
      var newObj = createModel(obj);
      return newObj.saveAsync();
    });
};

Upvotes: 3

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