'Cancel' for PromiseKit -- update MapKit cancellable code for Swift 4.2 and Xcode 10

Author: dougzilla32

Sources/MKDirections+Promise.swift

@@ -17,12 +17,12 @@ extension MKDirections {
 #if swift(>=4.2)
     /// Begins calculating the requested route information asynchronously.
     public func calculate() -> Promise<Response> {
-        return Promise { calculate(completionHandler: $0.resolve) }
+        return Promise<Response>(cancellableTask: MKDirectionsTask(self)) { calculate(completionHandler: $0.resolve) }
     }
 
     /// Begins calculating the requested travel-time information asynchronously.
     public func calculateETA() -> Promise<ETAResponse> {
-        return Promise { calculateETA(completionHandler: $0.resolve) }
+        return Promise<ETAResponse>(cancellableTask: MKDirectionsTask(self)) { calculateETA(completionHandler: $0.resolve) }
     }
 #else
     /// Begins calculating the requested route information asynchronously.
@@ -58,6 +58,17 @@ private class MKDirectionsTask: CancellableTask {
 //////////////////////////////////////////////////////////// Cancellable wrappers
 
 extension MKDirections {
+#if swift(>=4.2)
+    /// Begins calculating the requested route information asynchronously.
+    public func cancellableCalculate() -> CancellablePromise<Response> {
+        return cancellable(calculate())
+    }
+
+    /// Begins calculating the requested travel-time information asynchronously.
+    public func cancellableCalculateETA() -> CancellablePromise<ETAResponse> {
+        return cancellable(calculateETA())
+    }
+#else
     /// Begins calculating the requested route information asynchronously.
     public func cancellableCalculate() -> CancellablePromise<MKDirectionsResponse> {
         return cancellable(calculate())
@@ -67,4 +78,5 @@ extension MKDirections {
     public func cancellableCalculateETA() -> CancellablePromise<MKETAResponse> {
         return cancellable(calculateETA())
     }
+#endif
 }

Sources/MKMapSnapshotter+Promise.swift

@@ -17,7 +17,7 @@ extension MKMapSnapshotter {
 #if swift(>=4.2)
     /// Starts generating the snapshot using the options set in this object.
     public func start() -> Promise<Snapshot> {
-        return Promise { start(completionHandler: $0.resolve) }
+        return Promise<Snapshot>(cancellableTask: MKMapSnapshotterTask(self)) { start(completionHandler: $0.resolve) }
     }
 #else
     /// Starts generating the snapshot using the options set in this object.
@@ -48,8 +48,15 @@ private class MKMapSnapshotterTask: CancellableTask {
 //////////////////////////////////////////////////////////// Cancellable wrapper
 
 extension MKMapSnapshotter {
+#if swift(>=4.2)
+    /// Starts generating the snapshot using the options set in this object.
+    public func cancellableStart() -> CancellablePromise<Snapshot> {
+        return cancellable(start())
+    }
+#else
     /// Starts generating the snapshot using the options set in this object.
     public func cancellableStart() -> CancellablePromise<MKMapSnapshot> {
         return cancellable(start())
     }
+#endif
 }