FindCallback.java

/*
 * Copyright (c) 2015-present, Parse, LLC.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */
package com.parse;

import java.util.List;

/**
 * A {@code FindCallback} is used to run code after a {@link ParseQuery} is used to fetch a list of
 * {@link ParseObject}s in a background thread.
 * <p/>
 * The easiest way to use a {@code FindCallback} is through an anonymous inner class. Override the
 * {@code done} function to specify what the callback should do after the fetch is complete.
 * The {@code done} function will be run in the UI thread, while the fetch happens in a
 * background thread. This ensures that the UI does not freeze while the fetch happens.
 * <p/>
 * For example, this sample code fetches all objects of class {@code "MyClass"}. It calls a
 * different function depending on whether the fetch succeeded or not.
 * <p/>
 * <pre>
 * ParseQuery<ParseObject> query = ParseQuery.getQuery("MyClass");
 * query.findInBackground(new FindCallback<ParseObject>() {
 *   public void done(List<ParseObject> objects, ParseException e) {
 *     if (e == null) {
 *       objectsWereRetrievedSuccessfully(objects);
 *     } else {
 *       objectRetrievalFailed();
 *     }
 *   }
 * });
 * </pre>
 */
public interface FindCallback<T extends ParseObject> extends ParseCallback2<List<T>, ParseException> {
  /**
   * Override this function with the code you want to run after the fetch is complete.
   * 
   * @param objects
   *          The objects that were retrieved, or null if it did not succeed.
   * @param e
   *          The exception raised by the save, or null if it succeeded.
   */
  @Override
  void done(List<T> objects, ParseException e);
}