Question

I am trying to write a method to return the current location. While I’m waiting a period of 30sec, 1 min, or 2 minutes (set in settings) I display an alert view. I allow the user to bypass the timer wait with an alertView button accepting the current accuracy which I will display and update in the alert view. My code has a couple of holes in it I need help with. Essentially, it is to know how to have the getCurrentLocation method wait on the timer. I can’t just use a delay because I plan to force the timer to expire if the user hits the button or if the location accuracy is met (this is checked in timer). Here is the code:

- (void)timerFireMethod {
    static int elapsedTime = 0;
    elapsedTime++;
    if (elapsedTime >= gpsTimeout) {
        [locationManager stopUpdatingLocation];
        elapsedTime = 0; // reset static variable
        // !!! How do I do the following !!!
        //  do something to allow getCurrentLocation to return
    }
    if ((currentLocation.horizontalAccuracy <= gpsDesiredAccuracy) & (currentLocation.verticalAccuracy <= 2*gpsDesiredAccuracy)) {
        [locationManager stopUpdatingLocation];
        elapsedTime = 0; // reset static variable
        //  do something to allow getCurrentLocation to return
    }
}

- (CLLocation *)getCurrentLocation {
    // check if current accuracy is good enough and return if true
    if ((currentLocation.horizontalAccuracy <= gpsDesiredAccuracy) & (currentLocation.verticalAccuracy <= 2*gpsDesiredAccuracy)) {
        [locationManager stopUpdatingLocation];
        return currentLocation;
    } else {
        // show alert with count down timer
        UIAlertView *gpsAlertView = [[UIAlertView alloc] initWithTitle:nil message:@"tbd put in timer and list location accuracy updates" delegate:self cancelButtonTitle:@"Continue With Current Accuracy" otherButtonTitles:nil];
        [gpsAlertView show];
        // start timer
        NSTimer *gpsTimer = [NSTimer scheduledTimerWithTimeInterval:1.0
                                                         target:self selector:@selector(timerFireMethod:)
                                                       userInfo:nil repeats:YES];

        // !!! How do I do the following !!!
        // wait for when timer expires,
        // the user to press "Continue With Current Accuracy" button (can force timer to expire?)   
        return currentLocation;
    }
}

Answer 1

The way to wait on any timer or for any accelerometer or user event is to simply exit the current method back to the UI run loop by using a return statement.

Anything you want done after the wait can go in the timer or event callback method.