iPhone 3.0 Compass: how to get a heading?
Asked Answered
P

3

6

I'm relatively new to Objective-C and really don't know much about it yet, so I apologise for what is probably a really amateurish question.

I'm trying to get the magnetic heading from CLHeading and CLLocationDirection. However I'm getting compile errors for this line of code:

locationLabel.text = [[[location course] magneticHeading] stringValue];

The errors are:

warning: invalid receiver type 'CLLocationDirection'  
error: cannot convert to a pointer type

I don't really understand what I'm doing wrong here. Please help!

Petrochemistry answered 25/6, 2009 at 12:53 Comment(0)
R
14

Here are the steps needed to use the compass.

1) check the availability: if the headingAvailable property of the location manager is YES, then you can use the compass.

2) use the location manager method -(void) startUpdatingHeading to begin receiving the information you are searching for

3) actually retrieve this information using the delegate method (do not forget to set yourself as the delegate)

 - (void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading

Hope this helps.

Rebeccarebecka answered 25/6, 2009 at 15:1 Comment(1)
For Google's sake: The headingAvailable property has been deprecated since iO4. There is now a headingAvailable class method that returns a boolean value.Chasechaser
W
3

magneticHeading is of CLLocationDirection type, which is simply a typedef for the primitive data type "double". In your example you are trying to send a message to something that is not an object ! You should simply format the double like so:

locationLabel.text = [NSString stringWithFormat:@"Heading %.3f", [[location course] magneticHeading]];

Washer answered 26/6, 2009 at 12:40 Comment(1)
Thanks, this was where I was getting really confused. I need to learn more about typedefs I guess.Petrochemistry
I
1

How are you allocating and initializing location? Make sure location is defined as a (CLLocationDirection *) and not just a (CLLocationDirection).

Illuminati answered 25/6, 2009 at 13:30 Comment(0)

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