Add TileLayer.withTilelayer static method to make sure the TileLayer …

…gets closed.

src/main/groovy/geoscript/layer/TileLayer.groovy

@@ -184,5 +184,18 @@ abstract class TileLayer<T extends Tile> implements Closeable {
     String toString() {
         this.name
     }
+
+    /**
+     * Use a TileLayer within a Closure and make sure it gets closed.
+     * @param tileLayer The TileLayer
+     * @param closure A Closure that takes the TileLayer
+     */
+    static void withTileLayer(TileLayer tileLayer, Closure closure) {
+        try {
+            closure.call(tileLayer)
+        } finally {
+            tileLayer.close()
+        }
+    }
 
 }

src/test/groovy/geoscript/layer/TileLayerTestCase.groovy

@@ -277,4 +277,16 @@ class TileLayerTestCase {
         }
     }
 
+    @Test
+    void withTileLayer() {
+        File file = new File(getClass().getClassLoader().getResource("states.mbtiles").toURI())
+        TileLayer.withTileLayer(new MBTiles(file)) { TileLayer layer ->
+            Tile tile = layer.get(4, 2, 3)
+            assertNotNull tile
+            assertEquals 4, tile.z
+            assertEquals 2, tile.x
+            assertEquals 3, tile.y
+            assertNotNull tile.data
+        }
+    }
 }