How to make my app alive to make the second queue finish its job? What I want
is:
- start program- start an external process from a thread (asynchronously)-
start another thread after 5 seconds to terminate the process from the other
thread- end program
That's all.
–Mr Bee
Pada Jumat, 6 Januari 2017 14:49, Shawn Erickson <[email protected]>
menulis:
It looks like you aren't keeping your app alive to allow the secondary queue
to reliably execute the closures you queue with it. It isn't really clear what
you want to attempt so it hard to suggest the correct way to do things.
-Shawn
On Thu, Jan 5, 2017 at 11:39 PM Mr Bee via swift-users <[email protected]>
wrote:
Hi all,
I'm currently still learning Swift 3. Now I'm playing around with GCD (grand
central dispatch). I'd like to start an external process using Process from an
asynced thread, and create another thread to stop that external process after
some times. Here's what I do…
import Foundationimport Dispatch
extension Process { func execute(command: String, currentDir: String = "~",
arguments: [String] = [], input: String = "") -> String { if !input.isEmpty
{ let pipeIn = Pipe() self.standardInput = pipeIn // multiple
inputs are separated by newline if let input = input.data(using:
String.Encoding.utf8) { pipeIn.fileHandleForWriting.write(input) }
} let pipeOut = Pipe() self.standardOutput = pipeOut
self.arguments = arguments self.launchPath = command
self.currentDirectoryPath = currentDir self.launch() let output =
pipeOut.fileHandleForReading.readDataToEndOfFile() self.waitUntilExit()
return String(data: output, encoding: String.Encoding(rawValue:
String.Encoding.utf8.rawValue))! }}
//print(Process().execute(command: "/bin/ls", arguments: ["-l"]))
var cmd = Process()
print("Starting...")
DispatchQueue.global(qos: .default).async { print("Executing...") let s =
cmd.execute(command: "/bin/ls", arguments: ["-l"]) print(s)}
DispatchQueue.global(qos: .default).asyncAfter(deadline: DispatchTime.now() +
.seconds(5)) { if cmd.isRunning { print("Terminating...")
cmd.terminate() }}
print("Done.")
The code doesn't work as expected. The execute() function itself works fine
(uncomment the call in the middle of the code), but I don't know why it doesn't
work if it's called from within DispatchQueue closure. Even if I call a much
more simple function —like a for loop— it doesn't work consistenly, sometimes
the loop is completed, but other times it's not.
Google didn't really help me because this topic is pretty rare I suppose. Could
anyone enlight me, how to make the code works as I expected? What did I do
wrong?
Thank you.
Regards,
–Mr Bee
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