nsoperation | 易学教程

NSOperation on the iPhone

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问题 I\'ve been looking for some concrete scenarios for when NSOperation on the iPhone is an ideal tool to use in an application. To my understanding, this is a wrapper around writing your own threaded code. I haven\'t seen any Apple demo apps using it, and I\'m wondering if I\'m missing out on a great tool instead of using NSThread . The ideal solution here would be to describe a use-case scenario for NSOperation and how you would use it to solve your problem(s). 回答1: Cocoa Is My Girlfriend has a

NSOperation and NSOperationQueue working thread vs main thread

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问题 I have to carry out a series of download and database write operations in my app. I am using the NSOperation and NSOperationQueue for the same. This is application scenario: Fetch all postcodes from a place. For each postcode fetch all houses. For each house fetch inhabitant details As said, I have defined an NSOperation for each task. In first case (Task1), I am sending a request to server to fetch all postcodes. The delegate within the NSOperation will receive the data. This data is then

Get notification when NSOperationQueue finishes all tasks

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问题 NSOperationQueue has waitUntilAllOperationsAreFinished , but I don\'t want to wait synchronously for it. I just want to hide progress indicator in UI when queue finishes. What\'s the best way to accomplish this? I can\'t send notifications from my NSOperation s, because I don\'t know which one is going to be last, and [queue operations] might not be empty yet (or worse - repopulated) when notification is received. 回答1: Use KVO to observe the operations property of your queue, then you can

Wait until swift for loop with asynchronous network requests finishes executing

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I would like a for in loop to send off a bunch of network requests to firebase, then pass the data to a new view controller once the the method finishes executing. Here is my code: var datesArray = [String: AnyObject]() for key in locationsArray { let ref = Firebase(url: "http://myfirebase.com/" + "\(key.0)") ref.observeSingleEventOfType(.Value, withBlock: { snapshot in datesArray["\(key.0)"] = snapshot.value }) } // Segue to new view controller here and pass datesArray once it is complete I have a couple concerns. First, how do I wait until the for loop is finished and all the network

Wait until swift for loop with asynchronous network requests finishes executing

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问题 I would like a for in loop to send off a bunch of network requests to firebase, then pass the data to a new view controller once the the method finishes executing. Here is my code: var datesArray = [String: AnyObject]() for key in locationsArray { let ref = Firebase(url: \"http://myfirebase.com/\" + \"\\(key.0)\") ref.observeSingleEventOfType(.Value, withBlock: { snapshot in datesArray[\"\\(key.0)\"] = snapshot.value }) } // Segue to new view controller here and pass datesArray once it is

NSOperation vs Grand Central Dispatch

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问题 I\'m learning about concurrent programming for iOS. So far I\'ve read about NSOperation/NSOperationQueue and GCD. What are the reasons for using NSOperationQueue over GCD and vice versa? Sounds like both GCD and NSOperationQueue abstract away the explicit creation of NSThreads from the user. However the relationship between the two approaches isn\'t clear to me so any feedback to appreciated! 回答1: GCD is a low-level C-based API that enables very simple use of a task-based concurrency model.