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javascriptes6-promise

Reusing an existing Promise object if exists

I have a Dialog object that will show, well, dialogs. There are many entry points to show dialogs, e.g. yesNo(), message(), confirm(), etc. However, all these methods basically call the same other method, called showSimpleDialog(title, message, buttons).

I'd like all these methods (showSimpleDialog too) to return a promise, but there's a snag:

yesNo() {
  return new Promise((resolve, reject) => {
    axios
      .get(......)
      .then(this.showSimpleDialog(...));
  }
}

As you can see, I am prevented in the above example from either returning the promise that showSimpleDialog would make or by passing the instanced Promise to showSimpleDialog.

The former is impossible because we're already in a different Promise by the time we have access to it. The latter because the Promise object itself is not yet available within the constructor. Well, technically, in this particular case it is (exactly because we're already in a different Promise), but some of my entry functions are synchronous, some asynchronous and I simply can't use the same code pattern to achieve the same effect in both cases.

I investigated the thing and I found this, but the author suggests the approach is flawed and archaic to begin with.

So, what would be the correct approach to return a functioning Promise from ALL entry points while the entry points would still be free to reusing each other's Promises?

Solution

  • If I understand correctly, this.showSimpleDialog(...) also returns a Promise, right?

    If you want yesNo() to return the Promise retunred by this.showSimpleDialog(...)

    yesNo() { 
    return axios
        .get(......)
        .then(()=>{ 
            return this.showSimpleDialog(...);
        });
}

    That being said, consider using async/await, especially when dealing with multiple sequential promises, if possible.