Proof that NSOperation.completionBlock is not being cleared.

operationCompletionBlock.swift

// Run this in an iOS playground. It works correctly on Mac.


import Foundation
import PlaygroundSupport


let page = PlaygroundPage.current
page.needsIndefiniteExecution = true

func test() {

    let op = Operation()
    op.completionBlock = {
        print(op.completionBlock)  // prints "Optional((Function))"
        DispatchQueue.main.asyncAfter(deadline: .now() + 1, execute: {
            print(op.completionBlock) // prints "Optional((Function))"
            
            op.completionBlock = nil
            print(op.completionBlock) // prints "nil"
            page.finishExecution()
        })
    }
    
    op.start()
}

test()


// On macOS, these all print `nil`, as expected

Reported this as rdar://32541724 - http://openradar.appspot.com/32541724

https://github.com/PSPDFKit-labs/radar.apple.com/tree/master/32541724%20-%20CompletionBlockClearingForNSOperation