Question

I’m working on an iOS app with Cocos2D and I’m running into a lot of situations where I want to do something with a slight delay so I use a line of code like this:

[self scheduleOnce:@selector(do_something) delay:10];

The stuff that happens in do_something is only one line of code though.
Is there a way for me to define the function right in that line where I schedule it?

When I used to program with jQuery this is similar in what I’m trying to achieve:

$("a").click(function() {
  alert("Hello world!");
});

See how function() is defined right there? Is there a way to do this in Objective-C?
Also, is there a name for this? For future searches? Because I find this hard to explain.

Answer 1

You can use dispatch_after to execute a block after a certain amount of time.

int64_t delayInSeconds = 2.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
    /* code to be executed on the main queue after delay */
});

I would refer to it as a time dispatched block.

EDIT: How to dispatch it only once.

static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
    /* code to be executed once */
});

So in your case:

static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
    int64_t delayInSeconds = 2.0;
    dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
    dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
        /* code to be executed on the main queue after delay */
    })
});