Update thread-safe implementation of 'state' to use atomic property.

- remove the need for using NSLock to update `state`
- remove the need for using NSLock to update `currentTask`
- add KVO dependencies from `state` -> `isFinished` & `isExecuting`

Mobile Buy SDK/Mobile Buy SDK/Operations/BUYOperation.h

@@ -28,8 +28,6 @@
 
 @interface BUYOperation : NSOperation
 
-- (void)locked:(dispatch_block_t)lockedBlock;
-
 - (void)startExecution;
 - (void)finishExecution;
 - (void)cancelExecution;

Mobile Buy SDK/Mobile Buy SDK/Operations/BUYOperation.m

@@ -33,22 +33,22 @@ typedef NS_ENUM(NSUInteger, BUYOperationState) {
 
 @interface BUYOperation ()
 
-@property (nonatomic, assign) BUYOperationState state;
-@property (nonatomic, strong) NSLock *lock;
+@property (atomic, assign) BUYOperationState state;
 
 @end
 
 @implementation BUYOperation
 
-#pragma mark - Init -
+#pragma mark - KVO -
 
-- (instancetype)init
++ (NSSet *)keyPathsForValuesAffectingIsExecuting
 {
-	self = [super init];
-	if (self) {
-		_lock = [NSLock new];
-	}
-	return self;
+	return [NSSet setWithObject:@"state"];
+}
+
++ (NSSet *)keyPathsForValuesAffectingIsFinished
+{
+	return [NSSet setWithObject:@"state"];
 }
 
 #pragma mark - Concurrent -
@@ -68,41 +68,6 @@ typedef NS_ENUM(NSUInteger, BUYOperationState) {
 	return self.state == BUYOperationStateFinished;
 }
 
-#pragma mark - Setters -
-
-- (void)locked:(dispatch_block_t)lockedBlock
-{
-	[self.lock lock];
-	lockedBlock();
-	[self.lock unlock];
-}
-
-- (void)setState:(BUYOperationState)state
-{
-	[self.lock lock];
-	
-	NSString *oldPath = BUYOperationStateKeyPath(self.state);
-	NSString *newPath = BUYOperationStateKeyPath(state);
-	
-	/* ----------------------------------
-	 * We avoid changing state if the new
-	 * state is the same or the operation
-	 * has been cancelled.
-	 */
-	if ([oldPath isEqualToString:newPath] || self.isCancelled) {
-		[self.lock unlock];
-		return;
-	}
-	
-	[self willChangeValueForKey:newPath];
-	[self willChangeValueForKey:oldPath];
-	_state = state;
-	[self didChangeValueForKey:oldPath];
-	[self didChangeValueForKey:newPath];
-	
-	[self.lock unlock];
-}
-
 #pragma mark - Start -
 - (void)start
 {
@@ -128,18 +93,7 @@ typedef NS_ENUM(NSUInteger, BUYOperationState) {
 
 - (void)cancelExecution
 {
-	[self finishExecution];
-}
-
-#pragma mark - State -
-
-static inline NSString * BUYOperationStateKeyPath(BUYOperationState state)
-{
-	switch (state) {
-		case BUYOperationStateFinished:  return @"isFinished";
-		case BUYOperationStateExecuting: return @"isExecuting";
-	}
-	return @"";
+	
 }
 
 @end

Mobile Buy SDK/Mobile Buy SDK/Operations/BUYRequestOperation.h

@@ -36,6 +36,7 @@ typedef BOOL (^BUYRequestOperationPollingHandler)(NSDictionary * _Nullable json,
 
 @property (strong, nonatomic, readonly, nonnull) NSURLSession *session;
 @property (strong, nonatomic, readonly, nonnull) NSURLRequest *originalRequest;
+@property (strong, nonatomic, readonly, nonnull) BUYRequestOperationCompletion completion;
 
 @property (strong, nonatomic, nullable) BUYRequestOperationPollingHandler pollingHandler;
 

Mobile Buy SDK/Mobile Buy SDK/Operations/BUYRequestOperation.m

@@ -57,8 +57,7 @@ typedef void (^BUYRequestJSONCompletion)(NSDictionary *json, NSHTTPURLResponse *
 
 @interface BUYRequestOperation ()
 
-@property (strong, nonatomic) BUYRequestOperationCompletion completion;
-@property (strong, nonatomic) NSURLSessionDataTask *runningTask;
+@property (strong, atomic) NSURLSessionDataTask *runningTask;
 
 @end
 
@@ -112,21 +111,15 @@ typedef void (^BUYRequestJSONCompletion)(NSDictionary *json, NSHTTPURLResponse *
 			[self finishWithError:error response:response];
 		}
 	}];
-	[self locked:^{
-		self.runningTask = task;
-	}];
+	
+	self.runningTask = task;
 	[task resume];
 }
 
 - (void)cancelExecution
 {
 	[super cancelExecution];
-	
-	__block NSURLSessionDataTask *task = nil;
-	[self locked:^{
-		task = self.runningTask;
-	}];
-	[task cancel];
+	[self.runningTask cancel];
 }
 
 #pragma mark - Requests -
@@ -151,9 +144,7 @@ typedef void (^BUYRequestJSONCompletion)(NSDictionary *json, NSHTTPURLResponse *
 		 */
 		if (self.pollingHandler && self.pollingHandler(json, response, error)) {
 			NSURLSessionDataTask *task = [self requestUsingPollingIfNeeded:request completion:completion];
-			[self locked:^{
-				self.runningTask = task;
-			}];
+			self.runningTask = task;
 			[task resume];
 			
 		} else {