Question

Is it possible to run a selector which is invoked by the nstimer on the main thread?

The NSTimer is spawned in it’s own thread.

My structure is that a thread invokes a method with a nstimer, the nstimer invokes a method that do some updates, but I need these updates to happen on the main thread. What is the solution? Add another method and say performOnMainThread?

Answer 1

Yes, from your timer routine just call use performOnMainThread. From the docs:

Timers work in conjunction with run
loops. To use a timer effectively, you
should be aware of how run loops
operate—see NSRunLoop and Threading
Programming Guide. Note in particular
that run loops retain their timers, so
you can release a timer after you have
added it to a run loop.

also a caveat about invalidating repeating timers:

for a repeating timer, you must
invalidate the timer object yourself
by calling its invalidate method.
Calling this method requests the
removal of the timer from the current
run loop; as a result, you should
always call the invalidate method from
the same thread on which the timer was
installed