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[Operation] add willChangeValue() and didChangeValue() #836

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merged 3 commits into from Mar 23, 2017
Merged

[Operation] add willChangeValue() and didChangeValue() #836

merged 3 commits into from Mar 23, 2017

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ianpartridge
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Following on from the discussion on the swift-corelibs-dev mailing list, here's a PR to add willChangeValue() and didChangeValue() to Operation, in support of operations that are asynchronous from an operation queue.

@ianpartridge ianpartridge changed the title Operation: add willChangeValue() and didChangeValue() [Operation] add willChangeValue() and didChangeValue() Jan 24, 2017
phausler
phausler reviewed Jan 25, 2017
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Foundation/NSOperation.swift
@@ -47,7 +47,6 @@ open class Operation : NSObject {
#endif
}

/// - Note: Operations that are asynchronous from the execution of the operation queue itself are not supported since there is no KVO to trigger the finish.
open func start() {
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So the problem now is that if someone overrides main but not start and detaches from the current operation's queue.

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Can we document and live with that for now to unblock this particular use case?

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Any updates on this? The limitation @phausler identifies seems less serious than the current one.

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it seems like the lesser of two evils. so seems like a decent work-around until we have a better answer

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could you perhaps add a simple unit test to verify the expected behavior?

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@phausler @parkera I've added a test for this. Please could you review and run CI?

@parkera
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parkera commented Feb 17, 2017

@swift-ci please test

@alblue
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alblue commented Feb 22, 2017

There is a test failure on this - can you investigate and fix if necessary?

Test Case 'TestNSOperationQueue.test_AsyncOperation' started at 15:38:06.845
TestFoundation/TestNSOperationQueue.swift:80: error: TestNSOperationQueue.test_AsyncOperation : XCTAssertTrue failed - 
TestFoundation/TestNSOperationQueue.swift:81: error: TestNSOperationQueue.test_AsyncOperation : XCTAssertFalse failed -

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Will do. Race condition, I think.

phausler
phausler reviewed Feb 22, 2017
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TestFoundation/TestNSOperationQueue.swift Outdated

private let queue = DispatchQueue(label: "async.operation.queue")

private var _executing = false
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these two variables must be changed under the same lock

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Do you mean where they are updated at the end of the queue.async() block below?

What's the best way to do this? NSLock?

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NSLock should work, yes.

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@parkera Updated based on feedback - thanks. Please test and merge if you are happy.

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parkera commented Mar 21, 2017

@swift-ci please test

@ianpartridge
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@parkera tests passed 😄

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parkera commented Mar 23, 2017

Thanks!

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parkera commented Mar 23, 2017

@swift-ci test and merge

@swift-ci swift-ci merged commit bd53bb6 into apple:master Mar 23, 2017
@ianpartridge ianpartridge deleted the async-operation branch March 23, 2017 16:55
@rhyshort rhyshort mentioned this pull request Mar 23, 2017
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@ianpartridge ianpartridge mentioned this pull request Apr 12, 2017
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@ianpartridge @parkera @alblue @phausler @swift-ci