Selene is an iOS library which schedules the execution of tasks on a background fetch.

Installation

CocoaPods

Add to your Podfile: pod Selene

Submodule

You can also add this repo as a submodule and copy everything in the Selene folder into your project.

Use

1) Add the fetch background mode in your app’s Info.plist file.

2) Create a task

A task must conform to SLNTaskProtocol. For example:

@interface SampleTask: NSObject<SLNTaskProtocol>
@end

@implementation SampleTask

+ (NSString *)identifier {
  return NSStringFromClass(self);
}

+ (NSOperation *)operationWithCompletion:(SLNTaskCompletion_t)completion {
  NSOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
    // Do some work ....
    completion(UIBackgroundFetchResultNoData);
  }];
  return operation;
}

+ (CGFloat)averageResponseTime {
  return 5.0;
}

+ (SLNTaskPriority)priority {
  return SLNTaskPriorityLow;
}

@end

3) Add the task class to the scheduler

NSArray *tasks = @[[SomeTask class]];
// Run the scheduler every 5 minutes
[SLNScheduler setMinimumBackgroundFetchInterval:60 * 5];
// Add the tasks
[SLNScheduler scheduleTasks:tasks];

In the application delegate:

- (void)application:(UIApplication *)application performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {
  [SLNScheduler startWithCompletion:completionHandler];
}

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Interested? Here's the blog post