Position::Location.toDegrees() returns an array of objects

Former Member over 11 years ago

The API docs say it returns "An Array of the latitude and the longitude in degree format", and similar for .toRadians()

Looking at the return data it appears to return a 2-element array, but each element contains an object, rather than the number I'd expect. So this works:

var locs = info.position.toDegrees();

System.println("Latitude="+locs[0].toFloat());

System.println("Longitude="+locs[1].toFloat());

I think it would be helpful if the documentation was explicit about what the array was, and how to get at the lat/long numbers.

travis.vitek over 11 years ago

The elements of the array are indeed objects... of type Toybox.Lang.Double. The problem is that Double and Long aren't implicitly converted to string when you use them in a context that expects a string.

This code...

var n = 1;
var l = 1l;
var f = 1.0f;
var d = 1.0d;

Sys.println("n=" + n);
Sys.println("l=" + l);
Sys.println("f=" + f);
Sys.println("d=" + d);

produces the following output...

n=1
l=Obj: 2057992
f=1.000000
d=Obj: 2058312

If you use the value in a context that expects a numeric value, it all works out just fine.

Former Member over 11 years ago

Thanks, that's helpful. Is there any way of finding out what type an object is? Or do you have to guess?

travis.vitek over 11 years ago

This code will do the trick for most of the primitive built-in types.

function type_name(obj) {
    if (obj instanceof Toybox.Lang.Number) {
        return "Toybox.Lang.Number";
    }
    else if (obj instanceof Toybox.Lang.Long) {
        return "Toybox.Lang.Long";
    }
    else if (obj instanceof Toybox.Lang.Float) {
        return "Toybox.Lang.Float";
    }
    else if (obj instanceof Toybox.Lang.Double) {
        return "Toybox.Lang.Double";
    }
    else if (obj instanceof Toybox.Lang.Boolean) {
        return "Toybox.Lang.Boolean";
    }
    else if (obj instanceof Toybox.Lang.String) {
        return "Toybox.Lang.String";
    }
    else if (obj instanceof Toybox.Lang.Array) {
        return "Toybox.Lang.Array";
    }
    else if (obj instanceof Toybox.Lang.Dictionary) {
        return "Toybox.Lang.Dictionary";
    }
    else {
        return "???";
    }
}

Unfortunately, this code isn't extensible without making modifications to the original function, but it does work.

Travis

travis.vitek over 11 years ago

Just to be clear, the problem that you've stumbled into is a bug. It just isn't the bug that you thought it was.

Former Member over 11 years ago

That type_name() is really helpful - many thanks.

So the bug is that Double and Long aren't implicitly converted to string, but they should be (like Float and Integer)? Or ... ?

travis.vitek over 11 years ago

Yes. I believe that to be the case.

li2niu over 4 years ago

if (location) {

location = location.toDegrees(); // Array of Doubles.

gLocationLat = location[0].toFloat();

gLocationLon = location[1].toFloat();//invalid value??????????

Storage.setValue("_gLocationLat", gLocationLat);

Storage.setValue("_gLocationLon", gLocationLon);

}

How can it be???

_psx_ over 4 years ago in reply to li2niu

I'm very curious how often you save data to storage. No tests if data has changed, saving in 2 steps instead of saving array. Rather not optimised app,...

li2niu over 4 years ago in reply to _psx_

Every 20 mins

_psx_ over 4 years ago in reply to li2niu

even if nothing has changed...

and what happen with new location if-

- saving old location

- 1 minutes later location changesm - new location

- quit from watch face