On Feb 4, 2009, at 2:47 PM, Cem Karan wrote:

I know that we can only modify GUI elements from the main thread, but can we get the values for objects from other than the main thread? E.g., assume I have an editable NSTextField, and I have a worker thread. The user edits the field, clicks a button, and the main thread hands off the analysis to a worker thread. The worker thread then directly queries the NSTextField via its stringValue method. Is this kosher?

No.  First, NSTextField isn't on the list of thread-safe classes.

But quite aside from that, even if it were safe, you could not be sure the value you would get is the value you should get. It might have changed since the task was started.

In the scenario you describe, the button action method should marshal all of the inputs for the worker unit that's to be processed on the worker thread. Those inputs should be passed as integral parts of the work unit to the worker thread.

Cheers,
Ken

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