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Factory methods for Promise creation

Open njannink opened this issue 5 years ago • 2 comments

I added some factory methods to create the Promises. This prevents the need of casts in some Then(...) constructions:

old .Then(() => (IPromise) new Promise((resolve, reject) => ....))

new .Then(() => Promise.Create((resolve, reject) => ....))

njannink avatar Oct 18 '19 15:10 njannink

Looks good although could do with some unit tests and I'm not entirely sure if I understand the use-case for this. In the example you gave with a cast to an IPromise, the cast doesn't appear to do anything. It shouldn't matter in that case whether it's an IPromise or Promise because the chain of .Thens won't continue until the promise returned by the .Then callback has been resolved anyway. Also since Promise already implements IPromise there should never be any need to cast it to an IPromise. Is there something I'm missing here?

RoryDungan avatar Oct 21 '19 01:10 RoryDungan

The problem is with IPromiseOfT. If you want to convert that one to a Promise that doesn't do anything you run into problems at this moment if you want to convert that one in a Promise with no result. You then get a IPromise<Promise>

            IPromise promise = new Promise();

            IPromise<bool> boolPromise = promise.Then(() => new Promise<bool>());

            IPromise<Promise> wrapped = boolPromise.Then(b => new Promise((resolve, reject) =>
            {
                if (b)
                    resolve();
                else
                    reject(new Exception());
            }));

            IPromise good = boolPromise.Then(b => Promise.Create((resolve, reject) =>
            {
                if (b)
                    resolve();
                else
                    reject(new Exception());
            }));

I will add some tests

njannink avatar Oct 23 '19 15:10 njannink