Re: thread question

[Richard Frith-Macdonald]

On Thursday, December 27, 2001, at 06:03 PM, Aurelien wrote:

> Well, first I must admit that parts of my question come from a java 
> miscomprehension, things I haven't yet fully understood from my long 
> experience with this language.
>
> I am porting a project from java to objc and in the java project 
> there's an area that makes extensive uses of threads, and of course, 
> takes good care of synchronizing them.
>
> generally, I know how to handle code like this:
>
> synchronized void doSomething () {
>   // do something
> }
>
> -> I translate that into:
>
> - (void) doSomething
> {
>   NS(Recursive)Lock *aLock;
>   aLock = [[NS(Recursive)Lock alloc] init];
>   [aLock lock];
>   // do something
>   [aLock unlock];
> }
>
> so far, so good.

No .... the lock needs to be created beforehand. You could have a single 
global lock
created at the start of your program, and do something like this.

- (void) doSomething
{
  static NS(Recursive)Lock *aLock = nil;

  if (aLock == nil)
    {
      [globalLock lock];
      if (aLock == nil)
        {
          aLock = [[NS(Recursive)Lock alloc] init];
        }
      [globalLock unlock];
    }
  [aLock lock];
  // do something
  [aLock unlock];
}


> Now, what I don't understand is the use in java of the wait(), 
> notify () and notifyAll() methods.

There is really no direct equivalent ... but NSConditionLock should 
cover most of this I think.