When a callback is omitted from a DAO method, return a Promise that
resolves to the value normally passed to the callback of that method.
If a callback is provided, behave normally.
This API will use native ES6 promises if available. If not available,
or to force the use of another Promise library, you must assign the
global.Promise object.
e.g.:
global.Promise = require('bluebird')
Class methods affected:
- create
- updateOrCreate / upsert
- findOrCreate
- exists
- find
- findOne
- findById
- findByIds
- remove / deleteAll / destroyAll
- removeById / deleteById / destroyById
- count
- update / updateAll
Prototype methods affected:
- save
- delete / remove / destroy
- updateAttribute
- updateAttributes
- reload
Exceptions / edge cases:
- create() used to return the data object that was passed in, even if
no callback was provided. Now, if a callback is provided, it will
return the data object, otherwise it will return a Promise.
- If create() is provided an array of data objects for creation, it
will continue to always return the array. This batch creation mode
does not support promises.
- findOrCreate() has a callback of the form: cb(err, instance, created),
with the extra parameter indicating whether the instance was created
or not. When called with its promise variant, the resolver will
receive a single array parameter: [instance, created]