On Sep 7, 2008, at 9:33, Roman Kishchenko wrote:
Hi,
I am new to Cocoa and have been experimenting with NSRunLoop. I would
appreciate clarification about 'run' method semantics. The
documentation
states that:
"If no input sources or timers are attached to the run loop, this
method
exits immediately"
Yet, in my thread example below, the 'run' invocation blocks and
does not
exit. MyThread is a simple NSThread subclass. No custom input
sources or
timers are registered with the run loop. Unless I misunderstand the
documentation or there are some 'hidden' input sources or timers are
registered with the run loop, I would expect 'run' to exist
immediately.
Would much appreciate help with sorting this out!
Thanks,
Roman Kishchenko
@implementation MyThread
- (void)main {
NSLog(@"++ start");
NSRunLoop *loop = [NSRunLoop currentRunLoop];
[loop run];
NSLog(@"++ finish");
}
@end
_______________________________________________
This has come up before several times on this list over the years, so
there are a few answers already in the archives. But I have an idea
for a new way to explain it.
The documentation is correct. However, it's trying to warn you that
the method *can* return, not explain how to get it to return.
The mistake people make is in assuming that they control the contents
of a run loop (or even a run loop mode). However, the run loop is a
global object, accessible to all code run on that thread (and perhaps
other threads if you squirrel away a copy of the pointer somewhere).
In particular, all frameworks that you call into, directly or
indirectly, may access it and do things to it, including putting
things in it.
I think you are intuiting exactly this when you mention "custom" and
"hidden" input sources.
Try the -run...BeforeDate: method in a conditional loop if you want
block in the run loop most of the time, but want to bail under some
conditions (which would then be the test of the loop).
Chris Kane
Cocoa Frameworks, Apple
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