NSOperation Basics

Episode #175 | 17 minutes | published on June 26, 2015

Subscribers Only

nsoperation

In this episode we take a look at the basics of NSOperation, NSOperationQueue, starting from block operations and moving to custom NSOperation subclasses. We'll also see why it's important to make your operations thread safe.

This episode is part of a series: Deep Dive with NSOperation.

1. NSOperation Basics 17 min

2. Asynchronous Operations 17 min

3. NSOperation Dependencies 11 min

4. Advanced NSOperations 14 min

Episode Links

Creating an operation queue

 let operationQueue = NSOperationQueue()
 operationQueue.maxConcurrentOperationCount = 1  // makes this a serial queue

 operationQueue.suspended = true // use this if you don't want to automatically execute operations as they are added.

Adding a block operation

 let operation = NSBlockOperation(block: {
    println("executing")
 })
 operation.completionBlock = {
    println("Done executing")
 }
 operationQueue.addOperation(operation)

Creating an operation subclass

class FreeSpaceOperation : NSOperation {
    var fileSystemAttributes: NSDictionary?
    var error: NSError?

    let path: String

    init(path: String) {
        self.path = path
    }

    override func main() {
        let fileManager = NSFileManager.defaultManager()

        for i in reverse(1...5) {
            if cancelled {
                return
            }

            println("Sleeping \(i)...")
            sleep(1)
        }

        if cancelled {
            return
        }

        let attribs = fileManager.attributesOfFileSystemForPath(path, error: &error)
        println("attribs for \(path): \(attribs)")

        self.fileSystemAttributes = attribs
    }
}

View on Github

Download