po [NSThread currentThread]

Question

When I do po [NSThread currentThread], I got

{name = (null), num = 4}

When I look to the left I see: enter image description here

Looks like it's Thread number 6, not 4. Also what properties do we need to call to get that thread numbers anyway?

[NSThread currentThread].number? Doesn't exist though.

I found `(lldb) thread info` more useful. You could use the `tid` to connect output from Console.app / NSLog back to the thread. `thread #9: tid = 0x2e77, 0x0000000105293c9c` — rustyMagnet, May 11 '19 at 04:33

bbum · Accepted Answer · 2011-09-20T03:46:53.823

8

Thread numbers are meaningless, pretty much.

The thread instance, though, is a singleton per thread. You could use the NSThread's address, by coincidence. Better, still, would be to dip down to the mach_* API and grab the thread ID from that API.

[NSThread currentThread] is about as unique of a number as you'll get. If the thread terminates and then a new thread is created, you might see the same address vended. The mach APIs will vend something just about as unique, really.

What are you trying to do?

edited Sep 20 '11 at 03:46

answered Sep 19 '11 at 16:14

bbum

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If you need per-thread data, I think what you want is either `-[NSThread threadDictionary]`, or (at a lower level) `pthread_getspecific()`/`pthread_setspecific()`. – Jonathan Grynspan Sep 20 '11 at 03:49
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Yup -- that'd be the way to go if you want per-thread data. If you are trying to uniquely identify a thread, I might recommend generating a UUID and sticking it in the thread's dictionary. That way, when a thread is exited and a new thread created, there is no risk of collision. – bbum Sep 20 '11 at 04:15

score 2 · Answer 2 · answered May 14 '21 at 22:35

2

For Swift 5: It's a private variable, but accessible directly using keypath:

Thread.current.value(forKeyPath: "private.seqNum")!

answered May 14 '21 at 22:35

The Camster

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score -2 · Answer 3 · edited May 23 '17 at 12:30

-2

Here's the answer I posted to NSThread number on iOS?:

@implementation NSThread (ThreadGetIndex)

-(NSInteger)getThreadNum
{
    NSString * description = [ self description ] ;
    NSArray * keyValuePairs = [ description componentsSeparatedByString:@"," ] ;
    for( NSString * keyValuePair in keyValuePairs )
    {
        NSArray * components = [ keyValuePair componentsSeparatedByString:@"=" ] ;
        NSString * key = components[0] ;
        key = [ key stringByTrimmingCharactersInSet:[ NSCharacterSet whitespaceCharacterSet ] ] ;
        if ( [ key isEqualToString:@"number" ] || [ key isEqualToString:@"num" ] )
        {
            return [ components[1] integerValue ] ;
        }
    }
    @throw @"couldn't get thread num";
    return -1 ;
}

@end

edited May 23 '17 at 12:30

Community

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answered May 05 '14 at 04:04

nielsbot

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WARNING: It seems in iOS8 "num" has become "number" (and "number" and "name" have swapped orders... though the above code is fine for that) – Dave Owens Sep 13 '14 at 03:16
Useless answer, this method is only parsing the [NSThread description] and extracting the "number" value, the @Jim Thio question is completely different – Kappe May 13 '15 at 14:06
@DaveOwens Thanks, I changed the snippet – nielsbot May 13 '15 at 17:40

po [NSThread currentThread]

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