A collection of useful extras to make working with BFTaks more pleasant.

BFTaskImageView

An UIImageView subclass that allows you to set the image based on a task. When assigning the task it will execute and on completion update the image content.

BFTask* imageTask = [BFTask taskWithResult[UIImage imageNamed:@"name"];

BFTaskImageView* imageView;
imageView.task = imageTask;

BFTask+Timeout

Allows you to create tasks that expire after a certain interval. Useful for network operations. The tasks will error with domain=BFTaskErrorDomain and code = kBFTimeoutError. You can also use the convenience hasTimedOut property in BFTask. There are two ways to do this:

BFTaskCompletionSource

Create a BFTaskCompletionSource that expires after a set interval:

BFTaskCompletionSource *tcs = [BFTaskCompletionSource taskCompletionSourceWithExpiration:1];

[self someAsyncMethodWithCompletion:^(id result){
    // need to use trySetResult here because it could have expired!
    [tcs trySetResult:result];
}];

Now if you continue the task it will either complete or be cancelled after the specified timeout:

[tcs.task continueWithBlock:^id(BFTask* task){
    if(task.hasTimedOut){
        //timed out
    }
    else {
        // proceed as normal
    }
}];

Be sure to use the try methods to set result or error to cover the scenario your original tasks finishes after the timeout.

BFTask setTimeout

A faster way to do the above if you already have a BFTask is to use the setTimeout method then procceed with the continue block:

BFTask* someTask;

[[someTask setTimeout:20] continueWithBlock: ^id (BFTask *task) {
        if (task.hasTimedOut) {
            //timed out
        }
        else {
            // proceed as normal
        }
        return nil;
}];

BFTask+Result

If you are used to using blocks it can be cumbersome to typecast the result of a BFTask* everytime and can also lead to errors. If you need to check cancellation or exception or any other task properties then you should use the default methods, but if you are sure of the return type and want to quickly handle result and error cases this could be useful:

BFTask* someTask; // task that returns a string

[someTask continueWithResultBlock:^id(NSString* result, NSError *error) {
        //normal handling
        return nil;
 }];    

 //success block case:
 [someTask imageTask2 continueWithSuccessResultBlock:^id(NSString* result) {
        //normal handling
        return nil;
 }];

There are also methods that accept a BFExecutor parameter.

BFTask+Race

Creates a new task that is the result of the race between an array of tasks. Will complete when the first of the given tasks completes, faults or cancels. Inspired by the javascript Promise.race() feature.

BFTask* task1;
BFTask* task2;

BFTask* raceTask = [BFTask raceForTasks:@[task1, task2]];

BFTask+DuringBlock

An easy way to return a task that executes during a given block. The block is executed in a background queue.

// example of task during block;
[BFTask taskDuringBlock:^id {
    NSURL *url = [NSURL URLWithString:@"x.png"];
    NSData *imageData = [NSData dataWithContentsOfURL:url];
    UIImage *image = [UIImage imageWithData:imageData];
    return image;
}];

PS: If you return an NSError or NSException from the block, the resulting task will fail. You can also return a BFTask, in that case the resulting task will resolve based on the result of the returned task.

NSNotificationCenter+Bolts

An easy way to wait for a notification to be posted to notification center

[[[NSNotificationCenter defaultCenter] waitForNotificationNamed:UIApplicationDidEnterBackgroundNotification] continueWithSuccessBlock:^id _Nullable(BFTask<NSNotification *> * _Nonnull t) {
    // this only listens to notification once then removes observer
    return t;
}];

BFTaskCompletionSource Extras

There is a helper function to set a result or error for a given task source in a single line, really useful for wrapping methods with completion blocks:

BFTaskCompletionSource* tcs = [BFTaskCompletionSource taskCompletionSource];
[tcs setError:error orResult: result];

There is also a defaultClosure for wrapping methods that take a completion block with:

• A single error parameter => defaultErrorClosure
• A result (id) and an error parameter => defaultResultClosure.

For example, instead of:

[self loadStringAsync:^(NSString* result, NSError* error) {
    if(error) { 
        [tcs trySetError: error]; 
    } else { 
        [tcs trySetResult: result];
    }
}];

You can just do this:

[self loadStringsAsync:tcs.defaultResultClosure];

Usage

To view an example of all these tasks working together, view the sample application.

To run the example project, clone the repo, and run pod install from the Example directory first.

Feedback

New feature ideas, suggestions, or any general feedback is greatly appreciated.

Requirements

Installation

BFTask-Extras is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod "BFTask-Extras"

Author

Felix Dumit, [email protected]

License

BFTask-Extras is available under the MIT license. See the LICENSE file for more info.