Observables

Reference
Observables

Observables

The MongoDB Scala Driver is an asynchronous and non blocking driver. Using the Observable model asynchronous events become simple, composable operations, freed from the complexity of nested callbacks.

For asynchronous operations there are three interfaces Observable, Subscription and Observer.

Note

The interfaces are similar to Publisher, Subscription and Subscriber interfaces from the reactive streams JVM implementation. However, we prefer the name Observerable to Publisher and Observer to Subscriber for readability purposes.

Observable

The Observable represents a MongoDB operation which emits its results to the Observer based on demand requested by the Subscription to the Observable.

important

Observables can be thought of as partial functions and like partial functions nothing happens until they are called. An Observable can be subscribed to multiple times, with each subscription potentially causing new side effects eg: querying MongoDB or inserting data.

SingleObservable

Introduced in 2.0.0 the SingleObservable trait is an Observable implementation that will only return a single item. It can be used in the same way as ordinary Observables.