How to combine UIDatePicker with NSTimer

[jordanmeir]

how to set the time of UIDatePicker (count down) to a timer ??

[NSTimer scheduledTimerWithTimeInterval:(What i need to put here ?) target:self selector:@selector(Now) userInfo:nil repeats:NO];

[Domele]

The number you should put there is the interval at which you want the timer to fire. For example, if you specify 1, the timer will fire every second.

[jordanmeir]

i know how work a timer
but i want the UIDatePicker set the time...
how to do that ?

[Domele]

Oh sorry, UIDatePicker's have a NSTimeInterval named countDownTimer.

[jordanmeir]

its ok
if i have this:

-(void)Ten{
	//My action
}

how to use NSTimeInterval to do this "void"?

[Domele]

What is the method supposed to do?

[jordanmeir]

i want to do just like the Alarm clock app...
the UIDatePicker will set time to ring/show alert... and after the time was done it will to this action.

[Domele]

So you want to set an alarm with a date? Then use NSObject's performSelector:withObject:afterDelay:. To find the delay, find the time interval between the target date (your alarm date) and the current date using timeIntervalSinceNow on your target date.

Edit: On a related note, performSelector is basically the same thing as using a timer but timer's are usually for repeating things.

[jordanmeir]

can you give me an example or a link guide ?

[Domele]

Start off by getting the time interval by calling timeIntervalSinceNow on the date you get from the date picker. Post the code for that.

[jordanmeir]

i am a beginner of xcode and i have no idea how to begin...

[Domele]

Okay so you don't know how to retrieve the date from the UIDatePicker? Okay well a UIDatePicker has a NSDate property named date. To access properties, there are two ways. Since properties automatically generate setters and getters named after the ivar name, you can access it by calling the ivar name on the object.

AnObject *object = [anotherObject theIvarName];

Of course you can customize the name of the generate setter but for now, just assume you can't.

Another way is use dot notation. The format for dot notation is anObjectPointerName.theIvarName.

So try to get a date from the UIDatePicker.

[jordanmeir]

It's complicated for me...
i can't understand
Can you get me a simple example ? or a guide or a project example ?

[Domele]

Okay here is how you get a UIImage property named "image" from a UIImageView.

UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage named:"MyFakeImage.png"]];
UIIMage *imageInImageView = imageView.image;

Now do the same for your UIDatePicker but don't alloc it like I did because you'll be creating a new instance and that's not what we want. You need to get a reference to you existing date picker. If it's created in IB, setup an IBOutlet connection and if not, make an ivar. If you still have no idea, look at this tutorial on how to use a UIDatePicker: iPhone UIDatePicker Tutorial | James Sasitorn. It will show you how to retrieve the date.

Edit: I feel nice and I'm going to explain how to do what you're after.

NSDate *alarmFireDate = datePicker.date;

See how it follows pointerName.ivarName.

Then you need to get in seconds, how long this date is away from the current date.

NSDate *alarmFireDate = datePicker.date;
NSTimeInterval *differenceFromNow = [alarmFireDate timeIntervalSinceNow];

To call a method on an object, you surround it with brackets and type out the method name. [yourObject theMethodName];

Then you use the difference to tell your view controller or whichever object is managing your alarms to call a method once we reach our fire date. This object will need to stay alive otherwise the alarm will not fire.

NSDate *alarmFireDate = datePicker.date;
NSTimeInterval *differenceFromNow = [alarmFireDate timeIntervalSinceNow];
[yourObjectThatHandlesAlarms performSelector:@selector(theMethodThatWillGetCalledWhenTheAlarmDateIsReached) withObject:nil afterDelay:differenceFromNow];

That will make your object that handles alarm call the method "theMethodThatWillGetCalledWhenTheAlarmDateIsReach ed" on itself.

- (void)theMethodThatWillGetCalledWhenTheAlarmDateIsReached {
//show the user that the alarm has fired or whatever you want to do
}

[jordanmeir]

thank you
now i understanding...

now how to do the NSTimeInterval ?

[Domele]

"do the NSTimeInterval"? I think you'd need the object's consent first and it doesn't have a method for that unfortunately.

[jordanmeir]

now when i the label show me the date(iPhone UIDatePicker Tutorial | James Sasitorn)

i want that do an action when the time is done.



edit: i didn't see your edit and your example...

[Domele]

Okay so use a NSDateFormatter. Allocate it. Set the format string. Format codes can be found here: Stepcase Blog Archive Format String for the iPhone NSDateFormatter. Then use stringFromDate: using the alarm date as the argument. Example can be found here: Date Formatter Examples – Take 1: NSDateFormatter

[jordanmeir]

ok, i found an other way to do that...
thank you very much