Question

I have working snippet along the lines of:

for (UIButton *b in buttonMapping) {
    [b setTitle:@"yo!" forState:UIControlStateNormal];
    [NSThread sleepForTimeInterval:1.0];
}

There’s four buttons, all four buttons update. However, instead of updating one per second, four seconds go by & they all update.

How can I force UIButton to update? Or is this not the recommend method for sleeping?

Answer 1

[b setNeedsDisplay];

I’d also not recommend sleeping the main thread (like you’re doing here), since that disables all user interaction.

There are a couple of alternatives. One might be to use an NSTimer to execute a particular method once a second. However, the easier method would be to do something like:

for (NSUInteger idx = 0; idx < [buttonMapping count]; idx++) {
  UIButton * b = [buttonMapping objectAtIndex:idx];
  [b performSelector:@selector(setNormalStateTitle:) withObject:@"yo!" afterDelay:(idx*60)];
}

Then add a method to UIButton (ie, a category) called setNormalStateTitle: that simply executes the setTitle:forControlState: method. With this approach, you won’t need the setNeedsDisplay method at all.