Live Queries

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    Description — Couchbase mobile database live query concepts

    Overview

    A live query stays active and monitors the database for changes. A live query is a great way to build reactive user interfaces, especially table/list views, that keep themselves up to date. For example, as the replicator runs and pulls new data from the server, a live query-driven UI will automatically update to show the data without the user having to manually refresh. This helps your app feel quick and responsive.

    CBLQuery *query = [CBLQueryBuilder select:@[[CBLQuerySelectResult all]]
                                         from:[CBLQueryDataSource database:database]];
    
    // Adds a query change listener.
    // Changes will be posted on the main queue.
    id<CBLListenerToken> token = [query addChangeListener:^(CBLQueryChange * _Nonnull change) {
        for (CBLQueryResultSet *result in [change results]) {
            NSLog(@"%@", result);
            /* Update UI */
        }
    }];
    
    // Start live query.
    [query execute: &error]; (1)
    1 To start a live query, you must call query.execute(). This will immediately execute the query and post the result to the change listener. When there’s a change it re-runs itself automatically, and posts the new query result to any observers (change listeners).

    The following example stops the live query with the token from the previous example.

    [query removeChangeListenerWithToken:token];