Struct dittolive_ditto::store::query_builder::PendingCollectionsOperation

pub struct PendingCollectionsOperation<'order_by> { /* private fields */ }

Use ditto.store().collections() to query information about Ditto collections themselves.

They allow chaining of further collections-related functions. You can either call exec on the object to get an array of Collections as an immediate return value, or you can establish either a live query or a subscription, which both work over time.

A live query, established by calling observe_local, will notify you every time there’s a change in the collections that the device knows about.

A subscription, established by calling subscribe, will act as a signal to other peers that the device connects to that you would like to receive updates from them about the collections that they know about.

Typically, an app would set up a subscribe in some part of the application which is long-lived to ensure the device receives updates from the mesh. These updates will be automatically received and written into the local store. Elsewhere, where you need to use this data, an observe_local can be used to notify you of the data, and all subsequent changes to the data.

Implementations

impl<'order_by> PendingCollectionsOperation<'order_by>

pub fn limit(&mut self, limit: i32) -> &mut Self

Limit the number of documents that get returned when querying a collection for matching documents.

pub fn offset(&mut self, offset: u32) -> &mut Self

Offset the resulting set of matching documents. This is useful if you aren’t interested in the first N matching documents for one reason or another. For example, you might already have queried the collection and obtained the first 20 matching documents and so you might want to run the same query as you did previously but ignore the first 20 matching documents, and that is where you would use offset.

pub fn sort(&mut self, sort_param: Vec<COrderByParam<'order_by>>) -> &mut Self

Sort the documents that match the query provided in the preceding find-like function call.

Documents that are missing the field to sort by will appear at the beginning of the results when sorting in ascending order.

pub fn exec(&self) -> Result<Vec<Collection>, DittoError>

Execute the query generated by the preceding function chaining and return the list of matching documents. This occurs immediately.

pub fn subscribe(&self) -> Subscription

Enables you to subscribe to changes that occur on a collection. Having a subscription acts as a signal to others that you are interested in receiving updates when local or remote changes are made to documents that match the query generated by the chain of operations that precedes the call to subscribe. The returned Subscription object must be kept in scope for as long as you want to keep receiving updates.

pub fn observe_local<Handler>( &self, handler: Handler, ) -> Result<LiveQuery, DittoError>

where Handler: CollectionsEventHandler,

Enables you to listen for changes that occur on a collection. This won’t subscribe to receive changes made remotely by others and so it will only fire updates when a local change is made. If you want to receive remotely performed updates as well then also call subscribe with the relevant query. The returned LiveQuery object must be kept in scope for as long as you want the provided Handler to be called when an update occurs.