Display NSArray at specific intervals - objective-c

Question

I have an NSArray that I would like to display each object at a specific time interval, for example:
NSArray *array = [NSArray arrayWithObjects:#"foo",#"bar",#"baz",nil];
and output it:
for (object in array) {
NSLog(#"%#", object);
// wait 3 seconds then show next object
}
so it should do this:
foo
... wait three seconds
bar
... wait three seconds
baz
... wait three seconds
repeat
how can i do this?

Answer 1

The simplest approach would be to use Blocks...
You can explore how to do this with a Blocks using third party categories such as :
https://github.com/zwaldowski/BlocksKit
As for a solution without blocks:
#property (nonatomic, strong) NSArray *myArray;
#property (nonatomic) NSInteger iteration;
- (void)awakeFromNib //Or equivalent method called when you want to start scheduling..
{
self.myArray = [NSArray arrayWithObjects:#"foo",#"bar",#"baz",nil];
self.iteration = 0;
[NSTimer scheduledTimerWithTimeInterval:3
target:self
selector:#selector(fireEvent)
userInfo:nil
repeats:YES]; //Will Fire every 3 seconds...
}
-(void)fireEvent
{
NSLog(#"%#", [self.myArray objectAtIndex:self.iteration]);
self.iteration++;
if (self.iteration>=self.myArray.count) self.iteration=0;
}
If you with to invalidate the timer after all elements from the array are shown. Do the following :
-(void)awakeFromNib //Or equivalent method called when you want to start scheduling..
{
self.myArray = [NSArray arrayWithObjects:#"foo",#"bar",#"baz",nil];
self.iteration = 0;
[NSTimer scheduledTimerWithTimeInterval:3
target:self
selector:#selector(fireEvent:)
userInfo:nil
repeats:YES]; //Will Fire every 3 seconds...
}
-(void)fireEvent:(NSTimer*)timer
{
NSLog(#">>>> %#", [self.myArray objectAtIndex:self.iteration]);
self.iteration++;
if (self.iteration>=self.myArray.count) {
self.iteration=0;
[timer invalidate];
}
}
NOTE: The latter code only adds a ':' to the #selector(fireEvent:). And reads the NSTimer reference in the fireEvent as a parameter.

Answer 2

Depending on the surrounding context, you might be able to do what you want by letting an NSRunLoop run for 3 seconds. Alternatively, and perhaps a bit safer and saner, you could use an NSTimer to run an action every 3 seconds.
I'd originally suggested breaking up the loop, logging the first element, then perform the same action on the rest of the array after a 3-second delay, using either something like performSelector:withObject:afterDelay: or dispatch_after, but as danielbeard pointed out, NSTimer provides a much more straight-forward way to cancel the action (cancellation is possible with the other methods, but requires planning and manual work).
Edit: If I were going to do this with an NSTimer, I'd probably use this NSTimer+Blocks category and do something like (untested code):
__block NSUInteger index = 0;
NSTimer *timer;
timer = [NSTimer scheduledTimerWithTimeInterval:3.0 block:^{
NSLog(#"%#", array[index]);
index++;
if (index >= [array count]) {
[timer invalidate];
}
} repeats:YES];