I am using sendAsynchronous request to receive data from multiple request at same time. It works great, i am able to load all the data. Even it is faster. But i want to cancel my request if the user cancels the request. so i have created a NSThread and using that thread i have created asynchronous request. When user clicks cancel button i just cancelled the thread.
But even after cancelling the thread the data is still getting loaded. So i want to stop those requests completely from loading data.
Even i used this,
[NSObject cancelPreviousPerformRequestsWithTarget:(id) selector:(selector) object:(id)]
but it doesn't work. Any help or suggestion will be appreciated.
Thanks in advance.
According to the documentation the NSUrlConnection class has it's own cancel method.
Note: Why are you using sendAsynchronousRequest in a own thread? The completion-handler will be executed when the request returns. While the request tries to reach the server and get an answer the main-thread shouldn't be blocked. I suggest to use either a synchronous request in a background thread or an asynchronous request in your main thread.
Also be aware, that your thread doesn't terminate just by calling [NSThread cancel]
Related
Suppose I have a NSURLSessionDataTask created for two tasks. Let's say I consecutively make calls to the tasks one after another, and that the response to the second task finishes while the first task response has not arrived. So, now I have the delegate DidFinishWithError running and processing the response for the second task. While the delegate is running, if the response for the first task arrives, what would happen to the delegate method?
Would it finish its method for the second task response (which came first) and then start all over from beginning to process the logic for the first task response?
I am wondering how it works. I tried it out and it seems in this kind of a situation, the call to the first task (which takes longer than the second task to respond back with data) is made again back to the server.
NSURLSession has a delegateQueue property, which you can set at creation time. All delegate methods will be called on this queue. If the queue is busy, then it will be like any other - methods won't be executed until the queue can take them.
In your example, the first completion handler would have to return before the second could be executed.
I have an asynchronous controller,
I know the action will work asynchronously (no other action wait for that) and returns after completion of the task.
So my question is how it is deferent from making an asynchronous Ajax request to an action.
I think both are same in result.
An async request from javascript is not the same as an async task on the server.
An async task from javascript is still processed synchronously on the server, and as such, you may encounter thread pool starvation on large applications.
Having an async request that is processed asynchronously on the server is different, it frees up the IIS thread to immediately process other requests while that request, either from javascript or a full post/get is processed in the background.
some reading may help
http://msdn.microsoft.com/en-us/library/ee728598(v=vs.98).aspx#processing_asynchronous_requests
Is it best to send a synchronous or an asynchronous request?
I'm sending a request to a server, asking for a list of files, which I would like the user to choose from.
Synchronous request does stop the application from any user action until it completes, because it runs in the main thread.
Asynchronous does not as it runs in other thread.
You should always use asynchronous requests as they do not block the thread they are called from. Instead they will call your delegate methods when the connection fails or succeeds. If you need to prevent the user from doing anything while the connection is running, use a HUD class like MBProgressHUD (check github).
You'd want to use asynchronous calls when you're calling from the Main Thread. Otherwise, the whole user interface will become unresponsive (i.e: freeze) until the server responds. (The user interface in maintained by the main thread).
You'd want to use synchronous calls when you're calling from another thread and you want it to wait until it has the response before continuing. If you've manually created a thread, calling asynchronous from this new thread would create a third thread.
Asynchronous means the "calling body" won't wait until the task is done.
Ok, here's my situation:
I've got an app which requires a user-account.
While you're doing stuff like writing new comments, creating new Posts or reading a thread, every call to the server runs on a separate thread.
More specifically: A new thread is created, makes a call to the server, gets an answer from the server and saves the items from the answer to the Core Data Store.
In order to do this, every thread creates his own insertionContext, but they all share the same storeCoordinator.
But there's one Problem:
When someone does a logout from his account, I have to delete the store,
so if he logs in with another account, the stuff from the other account isn't in the coreDataStorage anymore.
But in Order to delete the Store, I have to make sure that there aren't any background Threads running anymore, because once they try to to save their stuff, they are sure to crash the app, since the store isn't valid anymore.
To clarify: these background threads are NSOperations which are put in an NSOperationQueue and executed from there.
Now CoreData gives the NSOperationQueue a function called "cancelAllOperations" but according to the Documentation, running Operations aren't killed, but only send a cancel message...
How do I use this cancel Message o_O
So far i'm checking at some points whether my thread is canceled and if it is, I don't execute other stuff, but if I do stuff like:
NSError *saveError = nil;
if(!self.isCanceled)
[insertionContext save:&saveError];
There is still the possibility that the Thread is being canceled between the if-check and the save.
So my question:
How do I handle this properly? Is it a question of properly canceling the thread?
I think you should not cancel any operations since it does not kill the thread immediately. Why don't you manage all operations that are currently being executed? This way you can postpone persistent store deletion until all tasks complete (or delete it immediately if there are no operations in progress).
I have a web request that can take 30-90 seconds to complete in some cases(most of the time it completed in 2-3). Currently, the software looks like it has hung if the request takes this long.
I was thinking that I could use background worker to process the webrequest in a separate thread. However, The software must wait on the request to process before continuing. I know how to setup the background worker. What I am unsure about is how to handle waiting on the request to process.
Do I need to create a timer to check for the results until the request times out or is processed?
I wouldn't use a timer. Rather, when the web request completes on the worker thread, use a call to the Invoke method on a control in the UI to update the UI with the result (or send some sort of notification).