iOS上线程功能的参数

Question

I was testing with a thread function. But the program always feedback an error. I guess that the error probably have something to do with the argument of the thread function, but i've no idea how to fix it. Thx in advance! The code is like:

-(void) doSomething:(id)p
{
   if((int)p == 100)
      NSLog(@"100");
   else
      NSLog(@"101");
}

int a = 100;
[self performSelectorInBackground:@selector(doSomething:) withObject:a];

Answer 1

Please read the docs for performSelectorInBackground:withObject: . a isn't an object, it's a primitive type.

You need to wrap the value in an NSNumber .

-(void) doSomething:(NSNumber *)p
{
   if([p intValue] == 100)
      NSLog(@"100");
   else
      NSLog(@"101");
}

int a = 100;
[self performSelectorInBackground:@selector(doSomething:) withObject:@(a)];

Or you can use GCD:

-(void) doSomething:(int)p
{
   if(p == 100)
      NSLog(@"100");
   else
      NSLog(@"101");
}

int a = 100;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    [self doSomething:a];
});

Answer 2

you should do something like

[self performSelectorInBackground:@selector(doSomething:) withObject:[NSNumber numberWithInt:a]];

as withObject takes only object and int is primitive datatype.