```
var sources = [internal, external1, external2];
function doStuff (e) {
// likely check if it's the right kind of error;
var url = sources.shift();
if (typeof url === 'undefined) {
return Promise.reject(new Error('out of sources'));
}
return get(url).then(check).catch(doStuff);
}
```
On Thu, May 15, 2014 at 10:52 AM, Michaël Rouges
<[email protected]>wrote:
> I don't pretend that impossible to do with current promises.
>
> I'm just saying that we can get a complexity that could be easily avoided.
>
> And a catch/then doesn't allow to return in the first promise onFulfilled,
> without embedded promises.
>
> I think a practical example might better illustrate the thing.
>
> Imagine, we have to check a data integrity, firstly internal, or from
> external sources, if the internal data is corrupted.
>
> The integrity controller is a foreign promisable controller , with a
> custom hash method & a fingerprint... we can't touch it.
>
>
> ```
> var foreignController;
>
> foreignController = (function () {
> var fingerPrint,
> hash,
> controller;
>
> fingerPrint = 'aforeignfingerprint';
>
> hash = function hash(data) {
> // foreign ownmade hash calculator
> };
>
> controller = function controller(resolve, reject, negociate) {
> var data,
> isValid,
> sources;
>
> data = this.data;
> isValid = fingerPrint === hash(data);
>
> if (isValid) {
> return resolve(data);
> }
>
> sources = this.sources;
>
> if (sources.length) {
> // not an error, we only remove that source
> // and try with the next one
> return negociate(sources.shift());
> }
>
> reject(new Error('No valid data found'));
> };
>
> return controller;
> }());
> ```
> Now, the data ownmade data checker :
>
> ```
> var getDataSync,
> onFulFilled,
> onRejected,
> onNegociated,
> handler,
> controller;
>
> getDataSync function getDataSync(source) {
> // data collector
> };
>
> onFulFilled = function onFulFilled(value) {
> // valid data treatment
> };
>
> onRejected = function onRejected(reason) {
> // no valid data found
> };
>
> onNegociated = function onNegociated(resolve, reject, negociate, retry,
> value) {
> var source;
>
> source = this.sources[0];
> this.data = getDataSync(source);
>
> console.log('data source corrupted : ' + value);
>
> retry();
> };
>
> handler = {
> data: 'some data',
> sources: ['internal', 'an.external.url', 'another.external.url', '...']
> };
>
> controller = foreignController.bind(handler);
>
> new Promise(controller)
> .then(onFulFilled, onRejected, onNegociated.bind(handler))
> /* a lot of thens */;
>
> ```
>
> Personnaly, I don't see how the current promises can solve it as simply.
>
>
> Michaël Rouges - https://github.com/Lcfvs - @Lcfvs
>
> _______________________________________________
> es-discuss mailing list
> [email protected]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
--
-Calvin W. Metcalf
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