Question

With objects, I can write an accessor to return nil if the object isn’t valid:

- (Weather *)howsTheWeather
{
    if (![WeatherNetwork isAvailable]) {
        return nil;
    }
    Weather *weatherNow = [WeatherNetwork getWeather];
    return weatherNow;
}

I’d like to do this with a CLLocationCoordinate2D, a struct for holding a latitude and longitude. I tried this:

- (CLLocationCoordinate2D)coordinate
{
    CLLocationCoordinate2D coord = CLLocationCoordinate2DMake(self.latitude, self.longitude);
    if (!CLLocationCoordinate2DIsValid(coord)) {
        return nil;
    }
    return coord;
}

But the compiler complains “Returning ‘void *’ from a function with incompatible result type ‘CLLocationCoordinate2D'”

What’s the best way to deal with this kind of situation? I was thinking of writing a separate method -(BOOL)isLocationValid:(CLLocationCoordinate2D)coordinate. Is there a better way to deal with this?

Answer 1

A struct cannot be null. You will need to go with option 2 (checking the validity of the struct based on the data it contains). Alternatively you could wrap your struct in an pseudo-object that is capable of being nil’ed, but that seems alot of work for spurious benefit.