firebase-ios-sdk/Firestore/Source/Public/FIRFirestoreSource.h

/*
 * Copyright 2018 Google
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#import <Foundation/Foundation.h>

/**
 * An enum that configures the behavior of `DocumentReference.getDocument()` and
 * `Query.getDocuments()`.  By providing a source enum the `getDocument[s]`
 * methods can be configured to fetch results only from the server, only from
 * the local cache, or attempt to fetch results from the server and fall back to
 * the cache (which is the default).
 *
 * Setting the source to `Source.default` causes Firestore to try to retrieve an
 * up-to-date (server-retrieved) snapshot, but fall back to returning cached
 * data if the server can't be reached.
 *
 * Setting the source to `Source.server` causes Firestore to avoid the cache,
 * generating an error if the server cannot be reached. Note that the cache will
 * still be updated if the server request succeeds. Also note that
 * latency-compensation still takes effect, so any pending write operations will
 * be visible in the returned data (merged into the server-provided data).
 *
 * Setting the source to `Source.cache` causes Firestore to immediately return a
 * value from the cache, ignoring the server completely (implying that the
 * returned value may be stale with respect to the value on the server). If
 * there is no data in the cache to satisfy the `getDocument[s]` call,
 * `DocumentReference.getDocument()` will return an error and
 * `QuerySnapshot.getDocuments()` will return an empty `QuerySnapshot` with no
 * documents.
 */
typedef NS_ENUM(NSUInteger, FIRFirestoreSource) {
  FIRFirestoreSourceDefault,
  FIRFirestoreSourceServer,
  FIRFirestoreSourceCache
} NS_SWIFT_NAME(FirestoreSource);