EarlGrey/Synchronization/GREYDispatchQueueTracker.h
//
// Copyright 2016 Google Inc.
//
// 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>
NS_ASSUME_NONNULL_BEGIN
/**
* A dispatch queue tracker for tracking dispatch queues.
*
* At most one tracker exists for each dispatch queue. The tracker will continue tracking the
* dispatch queue until the tracker or the tracker's underlying queue has been deallocated.
*/
@interface GREYDispatchQueueTracker : NSObject
/**
* Returns a tracker tracking @c queue. Creates a tracker only if one does not already exist.
*
* The tracked queue is held weakly so that it can be deallocated normally. The tracker will track
* the busy state of "zombie" queues that have been released by all external references but still
* have enqueued tasks that hold references to the queue.
*
* @param queue The queue that the returned tracker should be tracking.
*
* @return A tracker tracking @c queue.
*/
+ (instancetype)trackerForDispatchQueue:(dispatch_queue_t)queue;
/**
* @remark init is not an available initializer. Use the other initializers.
*/
- (instancetype)init NS_UNAVAILABLE;
/**
* Check for the idle state of the tracked dispatch queue.
*
* The tracked dispatch queue is considered busy if a tracked operation has not yet completed.
* @c dispatch_sync blocks and dispatch_sync_f tasks sent to @c queue are tracked.
* @c dispatch_async blocks and @c dispatch_async_f tasks sent to @c queue are tracked.
* @c dispatch_after blocks and @c dispatch_after_f tasks sent to @c queue are tracked if they are
* delayed no more than the delay amount set for the
* @c kGREYConfigKeyTrackableDispatchAfterDuration configuration.
*
* @return @c YES if the dispatch queue being tracked is idle, @c NO otherwise.
*/
- (BOOL)isIdleNow;
/**
* Check if the tracked queue still has external references.
*
* After all external references to a queue have been dropped, asynchronous tasks on the dispatch
* queue will still complete and the tracker will still report that it is busy until those tasks
* have completed. When the queue is only kept active by enqueued blocks, it is considered to be a
* zombie queue and not a live queue.
*
* @return @c YES if the dispatch queue being tracked no longer has external references, @c NO
* otherwise.
*/
- (BOOL)isTrackingALiveQueue;
@end
NS_ASSUME_NONNULL_END