On Mar 24, 2010, at 2:11 AM, Alexander Bokovikov wrote:
[[NSNotificationCenter defaultCenter] addObserver:anObj
selector:@selector(getData:)
name:NSFileHandleReadCompletionNotification
object:[[mytask standardError] fileHandleForReading]];
[[NSNotificationCenter defaultCenter] addObserver:anObj
selector:@selector(taskTerminated:)
name:NSTaskDidTerminateNotification
object:mytask];
[[[mytask standardError] fileHandleForReading] readInBackgroundAndNotify];
All is going OK when I have a progress bar in the main window, so anObj =
self. But I'd like to use just the same code to show a progress of the same
NSTask by a NSProgressIndicator, placed in a modal NSPanel, opened through
[NSApp runModalForWindow:]. In this case NSTask is launched and is executed
OK, And it does what it should. But none of notifications are going to my
popup modal window.At least getData method is never called, as debugger shows
it.
What is the problem reason? Is it possible to receive notifications in a
modal window?
There are two things going on, and you should be careful not to confuse them.
The first is the monitoring of external events or data sources, such as
reading from a pipe or monitoring the lifetime of the task. The second is
posting a notification.
In this case, both the file handle and the task object post notifications in
response to external events/data. However, the posting of the notification is
not the problem.
The problem is monitoring the external events/data. That is done via the
runloop. If you aren't running the runloop, or aren't running it in the
relevant modes, then those objects can never learn about the external events or
arrival of data. Since they haven't learned about them, they never even try to
post notifications about them.
You need to invoke -readInBackgroundAndNotifyForModes: and pass an array of
modes which includes NSModalPanelRunLoopMode (or NSRunLoopCommonModes, which
includes NSModalPanelRunLoopMode by default).
I'm not certain what modes NSTask uses to monitor for termination of the task.
Since -waitUntilExit runs the run loop in NSDefaultRunLoopMode, I assume it's
at least that mode. It may be only that mode, but it's not documented one way
or another. So, it's possible that an NSTask can't learn of the termination of
its task while the app is running a modal window.
If NSTask does monitor its task in NSModalPanelRunLoopMode, then the reason you
may not be getting the notification may be because the task itself is blocked.
It may have filled its output pipe. Since you're not reading from that pipe,
because the runloop is not running in the right mode for
-readInBackgroundAndNotify, the pipe is not getting drained. Once that the
pipe is full, the task will block when it tries to write to its output. So, it
never completes its work and never exits.
If that's the case, then fixing how you read from the pipe will fix both issues.
Regards,
Ken
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