ios - What does NSRunLoop do? -

i read many posts nsrunloop, this, this, this. can't figure out nsrunloop does

what see worker thread

wthread = [[nsthread alloc] initwithtarget:self selector:@selector(threadproc) object:nil];   [wthread start]; 

with nsrunloop inside it

- (void)threadproc  {     nsautoreleasepool* pool1 = [[nsautoreleasepool alloc] init];     bool isstopped = no;     nsrunloop *runloop = [nsrunloop currentrunloop];     [runloop addport:[nsmachport port] formode:nsdefaultrunloopmode];      while (!isstopped)     {         {             nsautoreleasepool* pool2 = [[nsautoreleasepool alloc] init];             [runloop runmode:nsdefaultrunloopmode                                       beforedate:[nsdate distantfuture]];              [pool2 release];         }     }      [pool1 release]; } 

and main thread passes work wthread

[self performselector:@selector(somework:) onthread:wthread withobject:nil waituntildone:no]; 

in term of passing work main thread worker thread, see many people this. why need nsrunloop here ? ?

i read nsrunloop used manage events, why there nothing except calling runmode inside threadproc ?

the example you've shown cocoa idiom creating thread continue run after method -threadproc exits. why?

because:

• the nsrunloop instance you've created has @ least 1 input source ([nsmachport port])
• you've explicitly started run loop runmode:beforedate

without adding input source , explicitly starting run loop, thread terminate.

parenthetically, although run loops still vital managing events , asynchronous tasks, not view nsthread default way of architecting asynchronous work in cocoa app nowadays. gcd far cleaner way of encapsulating background work.

edit:

submitting work serial queue in gcd:

@interface foo : nsobject @end  @implementation foo {     dispatch_queue_t _someworkerqueue; }  - (id)init {     self = [super init];     if( !self ) return nil;      _someworkerqueue = dispatch_queue_create("com.company.myworkerqueue", 0);     return self; }  - (void)performjob {     dispatch_async(_someworkerqueue, ^{         //do work asynchronously here     });      dispatch_async(_someworkerqueue, ^{         //more asynchronous work here     }); } @end