Processing only one request at a time in Alamofire?

Question

I want to process only one request at a time that on Alamofire - meaning when response come for first request it will process the second request and so on.

How to achieve this?

Answer 1

Basically u can select one from the few approaches:

1. Use NSOperationQueue - create queue with maxConcurrentOperationCount = 1, and simply add task in to queue. Sample:

   let operationQueue:NSOperationQueue = NSOperationQueue()
   operationQueue.name = "name.com"
   operationQueue.maxConcurrentOperationCount = 1
   operationQueue.addOperationWithBlock {  
       //do staff here
   }
   

   if u need to cancel all task - operationQueue.cancelAllOperations()

2. Use semaphore

   dispatch_semaphore_t semaphore = dispatch_semaphore_create(0)
   
   request.execute = {
       //do staff here    
       dispatch_semaphore_signal(sema)
   }
   
   dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER) //or 
   dispatch_semaphore_wait(semaphore, dispatch_time( DISPATCH_TIME_NOW, Int64(60 * Double(NSEC_PER_SEC)))) //if u need some timeout
   dispatch_release(semaphore)
   

3. GCD and DISPATCH_QUEUE_SERIAL

   let serialQueue = dispatch_queue_create("name.com", DISPATCH_QUEUE_SERIAL)
   
   func test(interval: NSTimeInterval) {
         NSThread.sleepForTimeInterval(interval)
         print("\(interval)")
   }
   dispatch_async(serialQueue, {
       test(13)
   })
   dispatch_async(serialQueue, {
       test(1)
    })
   dispatch_async(serialQueue, {
        test(5)
   })
   

4. Mutex - simple sample from here :

pthread_mutex_t mutex;
void MyInitFunction()
{
    pthread_mutex_init(&mutex, NULL);
}

void MyLockingFunction()
{
    pthread_mutex_lock(&mutex);
    // Do work.
    pthread_mutex_unlock(&mutex);
}

5. Use some kind of NestedChainRequests - make some class that will handle request one-by-one, example

6. Use PromiseKit (link) vs Alamofire (link)

The simplest approach I guess is to use GCD

Answer 2

You can create a dispatch queue or nsoprations and your alamofire task to it. Remember make a synchronous queue

This link might help you http://nshipster.com/nsoperation/