Casting CLLocationDistance in Swift
I am a complete newbie using Swift and have a headache trying to do something that should be pretty simple.
I have a Place object with a variable of type Double called distance. I am using the following code to store the distance between the user's location and some other locations:
var obj = res as Place
let loc = CLLocation(latitude: obj.location.lat, longitude: obj.location.lng)
let dist = CLLocation.distanceFromLocation(loc)
obj.distance = dist // ERROR
The last line shows an error: "CLLocationDistance is not convertible to" Double ". As far as I know, CLLocationDistance must be double. I tried to make this value double and float with
Double(dist)
and
obj.distance = dist as Double
but nothing works. I would appreciate any help.
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The reason this is happening boils down to the following line:
let distance = CLLocation.distanceFromLocation(loc)
It doesn't do what you think it does. distanceFromLocation
is an instance method, but you call it as a class method. Unlike ObjC, Swift allows it, but what you actually return, is not CLLocationDistance
, as a function of the following type signature: CLLocation -> CLLocationDistance
. You can check this by adding to the type annotation yourself:
let distance: CLLocation -> CLLocationDistance = CLLocation.distanceFromLocation(loc)
This is called private application and is beyond the scope of my answer, except that the first parameter of the function assigned distance
will be implicit self
when called as an instance method.
The fix is simple:
let distance = loc.distanceFromLocation(loc)
Then everything will work as you wish, at least in terms of the type system, because it correctly returns CLLocationDistance
which is substituted under Double
.
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You need two objects CLLocation
with two different locations
How fromLocation
andtoLocation
Then you get the distance in
let distance = fromLocation.distanceFromLocation(toLocation)
Example code for distance between old and new location:
func locationManager(manager: CLLocationManager!, didUpdateLocations locations: [AnyObject]!) {
if let firstLocation = locations.first as? CLLocation
{
mapView.setCenterCoordinate(firstLocation.coordinate, animated: true)
let region = MKCoordinateRegionMakeWithDistance(firstLocation.coordinate, 1000, 1000)
mapView.setRegion(region, animated: true)
if let oldLocation = oldLocation {
let delta: CLLocationDistance = firstLocation.distanceFromLocation(oldLocation)
totalDistane += delta
updateDistanceLabel()
}
oldLocation = firstLocation
}
}
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