diffusion/src/data/record/record-delta.js

Diffusion JavaScript client

var _interface = require('util/interface')._interface;

/**
 * {@link diffusion.datatypes.RecordV2} structural delta.
 * <p>
 * A RecordV2Delta describes the differences between two {@link diffusion.datatypes.RecordV2}
 * values. Unlike a {@link diffusion.datatypes.BinaryDelta binary delta}, a structural delta
 * can be queried to determine its effect. The
 * {@link diffusion.datatypes.RecordV2Delta#changes} method provides details of which values
 * have changed.
 *
 * <p>
 * An instance can be created from two RecordV2 values using
 * {@link diffusion.datatypes.RecordV2#diff(RecordV2)}.
 *
 * <p>
 * RecordV2Deltas are useful for identifying small changes to complex RecordV2
 * values. Here's any example of how to use this class to filter interesting
 * changes from a value stream.
 * <pre>
 * var datatype = diffusion.datatypes.recordv2();
 *
 * session.subscribe("topic").asType(datatype).on('value', (path, spec, newValue, oldValue) => {
 *     var schema = datatype.parseSchema(spec.properties.SCHEMA);
 *
 *     newValue.diff(oldValue).changes(schema).forEach((change) => {
 *         if (change.fieldName === "address") {
 *             // Do something with the changed address
 *             console.log(newValue.getFields());
 *         }
 *     });
 * });
 * </pre>
 *
 * @author Push Technology Limited
 * @since 6.0
 * @see diffusion.datatypes.RecordV2#diff
 * @class diffusion.datatypes.RecordV2Delta
 * @since 6.0
 */
module.exports = _interface('RecordV2Delta', [
    /**
     * Returns a list of the changes represented by the delta with reference to
     * a specified schema.
     * <P>
     * The schema supplied must comply with the data format of the delta. No
     * validation takes place, so if the schema does not match the data then the
     * results may be unpredictable.
     *
     * @param {diffusion.datatypes.RecordV2.Schema} schema - the schema
     * @return {Array<diffusion.datatypes.RecordV2Delta.Change>} the list of changes
     */
    'changes'
]);

/**
 * Represents a single change to a Record value.
 *
 * @typedef diffusion.datatypes.RecordV2Delta.Change
 * @property {String} recordName - The name of the affected record
 * @property {Number} recordIndex - The index of the affected record
 * @property {String} fieldName - The name of the affected field
 * @property {Number} fieldIndex - The index of the affected field
 * @property {String} key - Returns the string key representation of the affected item in
 * the form recordName(recordIndex).fieldName(fieldIndex).
 * @property {String} type - String denoting the type of change that this represents
 */