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SwiftQueue is a library built on top of Operation and OperationQueue that allows you to specify run and retry constraints to your jobs.

Getting started

SwiftQueue is available on CocoaPod repository. There is no support for Carthage yet.

pod 'SwiftQueue'

Tweet sending job queue

In the following example we will create step by step tweet sending that use SwiftQueue to keep tweets ordering.

Create your first Queue

Each queue you will create will run independently. SwiftQueue only requires 1 argument, an array of creator. See Job Creation section. You can also specify an identifier to your queue by using the convenience initialiser

let tweetQueueManager = SwiftQueueManager(creators: [TweetJobCreator()])

Insert job info to the queue

// Type is required to know which implementation of Job we should create
JobBuilder(type: SendTweetJob.type)
        // Prevent adding the same job multiple times
        .singleInstance(forId: String)
        // Different group name will run in parallel
        // But one by one for a group
        .group(name: "tweet")
        // Sending tweet will require internet. At least cellular. 
        // Will also be executed if connected to wifi.
        .internet(atLeast: .cellular)
        // Content of your tweet. Can be a class, struct or anything
        .with(params: "Hello TweetWorld")
        // Retry maximum 5 times if the job fail before removing from the queue
        // No retry by default
        .retry(max: 5)
        // Insert to queue
        .schedule(manager: tweetQueueManager)

Write your job execution code

class SendTweetJob: Job {
    
    public static let type = "SendTweetJob"

    private let tweetMessage: String

    // Argument specified in JobBuilder.with()
    required init(message: String) {
        self.tweetMessage = message
    }

    func onRunJob(callback: JobResult) throws {
        // Actual sending is happening here
        API.sendTweet(type: "TEXT", content: tweetMessage)
        .onSucess {
            // Notify job done without error
            callback.onDone(error: nil)
        }.onFail { error in
            // Job failed.
            callback.onDone(error: error)
        }
    }

    func onError(error: Error) -> RetryConstraint {
       // When a job failed. Since we put retry(max: 5). 
       // This callback will be called at most 5 times
       // Specify if we still want to retry or not.
        if error is ApiError {
            // No need for retry, Server rejected the message.
            // Will remove job from queue even if retry counter > 0
            return RetryConstraint.cancel 
        } else {
            // Job will run again. Retry counter will decrease
            return RetryConstraint.retry
        }
    }

    func onComplete() {
        // Job is removed from queue and successfully ran
        // Update your UI or your database
    }

    func onCancel() {
        // Job is removed from queue but the job failed.
        // Can be due to deadline, retry count reach limit, or RetryConstraint.cancel
        // Update your UI or your database
    }
}

Last step, Linking

class TweetJobCreator: JobCreator {

    func create(type: String, params: Any?) -> Job? {
        // params as specified in JobBuilder.with()
        if type == SendTweetJob.type, let message = params as? String  {
            // Return our actual job.
            return SendTweetJob(message: message)
        } else {
            // Nothing match
            return nil
        }
    }
}