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@bnickel
Last active June 23, 2020 16:33
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Swift retry operation playground
import Foundation
protocol Completable {
func addCompletionOperation(on queue: OperationQueue, complete: @escaping (Self) -> Void) -> Operation
}
extension Completable where Self: Operation {
func addCompletionOperation(on queue: OperationQueue, complete: @escaping (Self) -> Void) -> Operation {
let completionOperation = BlockOperation {
complete(self)
}
completionOperation.addDependency(self)
queue.addOperation(completionOperation)
return completionOperation
}
}
protocol Enqueueable {
func enqueue(in queue: OperationQueue) -> Self
}
extension Enqueueable where Self: Operation {
func enqueue(in queue: OperationQueue) -> Self {
queue.addOperation(self)
return self
}
}
final class NetworkOperation: BlockOperation, Completable, Enqueueable {
var result: (URLResponse, Data)?
var lastError: Error?
init(url: URL, attemptLimit: Int) {
super.init()
addExecutionBlock { [weak self] in
for _ in 1 ... attemptLimit {
let request = URLRequest(url: url)
do {
var response: URLResponse?
let data = try NSURLConnection.sendSynchronousRequest(request, returning: &response)
self?.result = (response!, data)
return
} catch { self?.lastError = error }
}
}
}
}
let networkQueue = OperationQueue()
let completionQueue = OperationQueue()
NetworkOperation(url: URL(string: "https://google.com")!, attemptLimit: 5)
.enqueue(in: networkQueue)
.addCompletionOperation(on: completionQueue) { operation in
if let (response, data) = operation.result {
dump(response)
dump(data)
} else if let error = operation.lastError {
dump(error)
} else {
dump("¯\\_(ツ)_/¯")
}
}
// Let the playground finish.
completionQueue.waitUntilAllOperationsAreFinished()
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