SetNeedsDisplay not working

Question

I saw many threads related to this issue, but none addresses my case (I think).

My case should be simple, I have a Custom UIView in my controller, from my controller, I use the [ self.myView setNeedsDisplay ] and it works perfectly.

I'm having problems when Im trying to call this from inside of the UIView itself...I have a notification being sent from another class, and it is being received by my View (this works) with the information it passes, I update internal properties of this view and than I'm calling the [self setNeedsDisplay ] wishing to have my screen updated with the new states, but nothing is happening, I used a NSLOG inside my drawRec method, and it is not being called at this time, it is only called when my controller class call the setNeedsDisplay , and when that happens, the update that should have happened before is showed on screen... I don't know why its not updating before...

Here are some code:

My controller asking for update: (works OK!)

- (void)addNodeToNetwork:(DTINode *)node
{
[self.myNetwork addNodeInTheNetwork:node];
self.gridView.nodesToDraw = [self.myNetwork.nodesInNetwork copy];

CGRect tempRec = CGRectMake(node.nodePosition.x, node.nodePosition.y node.nodePosition.x, node.nodePosition.y);
NSValue *rectObj = [NSValue valueWithCGRect:tempRec]; //transforma o cgrect num objeto

[self.gridView.fatherNodes setValue:rectObj forKey:node.nodeName];
[self.gridView setNeedsDisplay];
}

My notification method trying to update my drawing: (Not Working ! )

- (void) receiveTestNotification:(NSNotification *) notification
{
NSDictionary *userInfo = notification.userInfo;
DTINode *notificationNode = [userInfo objectForKey:@"myNode"];
NSLog(@"Im Here!");
for (DTINode *node in self.nodesToDraw)
{
    NSLog(@"Here too");

    if(node.nodeName == notificationNode.fatherNode)
    {
        CGRect temp = CGRectMake(notificationNode.nodePosition.x, notificationNode.nodePosition.y, node.nodePosition.x, node.nodePosition.y);
        NSValue *tempObj = [NSValue valueWithCGRect:temp];
        [self.fatherNodes setObject:tempObj forKey:notificationNode.nodeName];
        [self setNeedsDisplay];
        NSLog(@"Should REDRAW NOW!"); // It print this but no drawing is made!
    }
}
}

I'm not pasting my drawRect here because it works, the problem is that is is not being called from inside my UIView setNeedsDisplay !

Anyone have any idea why this is not working????

Answer 1

After alot of testing, I saw something related to threads and the fact setNeedsDisplay should only be called in the mainThread...besides I never started a separeted thread in this classes, the class that raised the Notification was in a secondary thread...and aparently this was causing the issue...

to Solve it I just forced setNeedsDisplay to be called in the main thread..

dispatch_async(dispatch_get_main_queue(), ^{
            [self setNeedsDisplay];  
});

Swift 3:

DispatchQueue.main.async { [weak self] in
    self?.setNeedsDisplay()
}

Answer 2

I think the correct way to use it is:

[self setNeedsDisplay:YES]; 

Although I always have problems to get that working :(