目标c线程中的线程变量寿命

Question

我有一个NSOperation，在它的主方法中我使用[NSThread detachNewThreadSelector:@selector(aMethod:) toTarget:self withObject:anArgument];

aObject（我的NSOperation子类的实例变量）是对-main方法内部返回的自动释放数组的对象的弱引用。。。

-(void)main {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    NSArray *clients = [group produceClients]; // clients array is an autorelease instance
    self->aObject = [clients objectAtIndex:3]; // a weak reference, Lets say at index three!
    [NSThread detachNewThreadSelector:@selector(aMethod:) 
                             toTarget:self 
                           withObject:@"I use this for another thing"];
    // Do other things here that may take some time
    [pool release];
}
-(void)aMethod:(NSString*)aStr {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    // aStr object is reserved for another functionality
    // I know that I could pass a NSDictionary with a number of entries, which would be
    // retained by `detachNewThreadSelector` but then ... 
    // I wouldn't have to ask this question ! :)
    // Do several things with aObject, which is a weak reference as described above.
    NSLog(@"%@", [self->aObject.id]);
    // Is it safe ?
    [pool release];
}

我知道NSThread的detachNewThreadSelector方法保留了self和withObject:anArgument，但aObject会发生什么？？是否确定在执行分离线程（aMethod:）的过程中会存在？Self被detachNewThreadSelector保留，这是否意味着-main线程的池将被延迟释放，因为它被保留了，因此clients将存在，从而aObject将存在
或者-main（NSOperation）线程将在-aMethod（NSThread）完成之前完成执行并释放，所以在那里使用aObject是不安全的？

真正的问题是：当从线程内部调用[NSThread detachNewThreadSelector:@selector(aMethod:) ...toTarget:self ...]时，最后一个线程是否以其自动释放的实例（clients数组）可以安全地在aMethod（self->aObject）中使用的方式保留（比方说通过弱引用）？

Answer 1

您的方法看起来非常不稳定，但我不是多线程专家，所以我可能错了。你的客户端数组在主自动释放池中，你不能保证它会等到你的aMethod线程完成耗尽。这个怎么样：

-(void)main {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    [NSThread detachNewThreadSelector:@selector(aMethod:) 
                             toTarget:self 
                           withObject:@"I use this for another thing"];
    [pool release];
}
-(void)aMethod:(NSString*)aStr {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    NSArray *clients = [group produceClients]; // clients array is an autorelease instance
    self->aObject = [clients objectAtIndex:3]; // a weak reference, Lets say at index three!
    [pool release];
}

使用这种方法，客户端数组位于线程的自动释放池中。