Execute cross thread function one by one - ios

Question

I have some special functions in my project, they will execute cross many threads, such as childContext perform block or AFNetwork response block:
(void)my_function {
dispatch_async(dispatch_get_main_queue(), ^{
NSManagedObjectContext *childContext = [[[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType] autorelease];
childContext.parentContext = self.managedObjectContext;
[childContext performBlock:^{
[self.operationManager POST:URL parameters:nil block:^(AFHTTPRequestOperation *operation, id responseObject) {
//Do something
[childContext performBlock:^{
//Do something
}];
}];
}];
});
}
Now I want to execute them one by one (including all blocks in function). After reading a couple of other answers, some of the Apple documentation, I get some answers:
1. NSRecursiveLock
I can add NSRecursiveLock for each function, but the issue is that I can't lock/unlock cross thread.
(void)my_function {
[MyLock lock]; // Lock here
dispatch_async(dispatch_get_main_queue(), ^{
NSManagedObjectContext *childContext = [[[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType] autorelease];
childContext.parentContext = self.managedObjectContext;
[childContext performBlock:^{
[self.operationManager POST:URL parameters:nil block:^(AFHTTPRequestOperation *operation, id responseObject) {
//Do something
[childContext performBlock:^{
//Do something
[MyLock unlock]; //Unlock here
}];
}];
}];
});
}
2. NSOperation
I can add each function to NSOperationQueue as a NSOperation, and set concurrent operation number to 1, but the issue is that I can't make sure the code in block has been executed even the NSOperation finishes successfully.
3. #synchronized
I can add #synchronized, but has same issue as NSOperation

Answer 1

My suggestion is using NSOperationQueue and Asynchronous NSOperation.
You can make sure operation execute one by one in two ways
addDependency:
Set maxConcurrentOperationCount to 1
With Asynchronous NSOperation,it is you to decide when this Operation is done.
For example
-(void)my_function {
dispatch_async(dispatch_get_main_queue(), ^{
NSManagedObjectContext *childContext = [[[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType] autorelease];
childContext.parentContext = self.managedObjectContext;
[childContext performBlock:^{
[self.operationManager POST:URL parameters:nil block:^(AFHTTPRequestOperation *operation, id responseObject) {
//Do something
[childContext performBlock:^{
//Do something
//Only mark this NSOperation is done when all task of this function is finished.
}];
}];
}];
});
}
How to make an Asynchronous NSOperation,This is what I usually do,you can also refer it in the document.
Keep two property
#interface AsyncOperation (){
BOOL finished;
BOOL executing;
}
Use these two property to manage Operation state
-(BOOL)isFinished{
return finished;
}
-(BOOL)isExecuting{
return executing;
}
3.Mark Operation start
Note:start function is called on the thread the Operation created
-(void)start{
if ([self isCancelled])
{
// Must move the operation to the finished state if it is canceled.
[self willChangeValueForKey:#"isFinished"];
finished = NO;
[self didChangeValueForKey:#"isFinished"];
return;
}
// If the operation is not canceled, begin executing the task.
[self willChangeValueForKey:#"isExecuting"];
[NSThread detachNewThreadSelector:#selector(main) toTarget:self withObject:nil];
executing = YES;
[self didChangeValueForKey:#"isExecuting"];
}
Mark Operation is done
I use this function
-(void)setOperationFinished{
[self willChangeValueForKey:#"isFinished"];
[self willChangeValueForKey:#"isExecuting"];
executing = NO;
finished = YES;
[self didChangeValueForKey:#"isExecuting"];
[self didChangeValueForKey:#"isFinished"];
}