IPOfflineQueue is a persistent, serial task queue for iOS. It's especially ideal for queuing actions that require an internet connection that may be slow or absent.

• You enqueue tasks to it, and they run whenever they can in a background thread.
• Tasks are always executed in the order in which they were added (FIFO).
• Tasks are not executed in parallel, although you are free to run parallel operations in your task-execution handler.
• Queued tasks persist between application launches.
• The application will remain running in the background until the queue completes or until iOS kills it (after no more than 10 minutes).
• You're welcome to operate multiple queue instances if you'd like to run different tasks.
• GCD is used extensively to prevent blocking the main thread.

If this is useful to you, please consider integrating send-to-Instapaper support in your app if it makes sense to do so. Details: http://www.instapaper.com/api

Really. Not even I'm using this in any shipping apps yet. Use at your own risk.

• Requires iOS 4.0 or greater.
• You must link libsqlite3.dylib with your project.

See ViewController.m in the sample project for a more detailed example, but it goes like this:

IPOfflineQueue *queue = [[IPOfflineQueue alloc] initWithName:@"main" delegate:self];

...

[queue enqueueActionWithUserInfo:myTaskDictionary];

...

- (IPOfflineQueueResult)offlineQueue:(IPOfflineQueue *)queue executeActionWithUserInfo:(NSDictionary *)userInfo
{
    // (try to do something)
    
    if (/* internet connection failed */) {
        return IPOfflineQueueResultFailureShouldPauseQueue;
    } else {
        return IPOfflineQueueResultSuccess;
    }
}

That's all you need to know about, really. (I hope.)

Copyright (c) 2011, Marco Arment All rights reserved.

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(You may know this as the New BSD License.)