Changes Support #24
Changes Support #24
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| @@ -124,6 +124,64 @@ couch.mango(dbName, mangoQuery, parameters).then(({data, headers, status}) => { | |||
| }); | |||
| ``` | |||
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| ## Trigger A Design Update | |||
| // either request error occured | ||
| // ...or err.code=EDOCMISSING if document is missing | ||
| // ...or err.code=EUNKNOWN if statusCode is unexpected | ||
| }); |
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It's a bit tricky API and it's more similar to publish-subscribe, than to promises which get fulfilled one time.
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I use the promise to return the result of the subscribe request, and the callback for the actual subscription.
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I mean exactly this. Promise represents the asynchronous operation which finishes either with some useful result (resolve) or fails with some error (reject). Publish/Subscribe (EventEmitter, Rx.Observable) represent continuous operations which can emit different events.
Is there any need for result of subscribe request? How should the callback code work if subscribe request fails?
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The callback is not invoked at all if the promise fails. We could return an interface that has a subscribe method in the promise, but then we would have to cache any intermediate data.
I think you need both the promise and subscription. There is an async operation and a separate subscription.
I guess we could send an error to the subscription if the connection fails; Then you would not need to return a promise at all. But that would break chaining operations, and make the API less consistent.
Request.js would not work in the browser, so we had to use XMLHttpRequest.
This is working very well in our production system.