Add expression accessors

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/style/layers/PropertyValue.java

@@ -5,6 +5,7 @@
 import android.support.annotation.Nullable;
 
 import com.mapbox.mapboxsdk.exceptions.ConversionException;
+import com.mapbox.mapboxsdk.style.expressions.Expression;
 import com.mapbox.mapboxsdk.style.functions.Function;
 import com.mapbox.mapboxsdk.utils.ColorUtils;
 
@@ -57,6 +58,31 @@ public boolean isValue() {
     return !isNull() && !isFunction();
   }
 
+  /**
+   * Returns if this is a expression.
+   *
+   * @return true if is a expression, false if not
+   */
+  public boolean isExpression() {
+    return !isNull() && value instanceof Expression;
+  }
+
+  /**
+   * Get the expression of the property.
+   *
+   * @return the expression value
+   */
+  @Nullable
+  public Expression<T> getExpression() {
+    if (isExpression()) {
+      // noinspection unchecked
+      return (Expression<T>) value;
+    } else {
+      Timber.e("not an expression, try value");
+      return null;
+    }
+  }
+
   @Nullable
   public Function<?, T> getFunction() {
     if (isFunction()) {

platform/android/MapboxGLAndroidSDKTestApp/src/main/java/com/mapbox/mapboxsdk/testapp/activity/style/SymbolGeneratorActivity.java

@@ -269,6 +269,11 @@ public void onDataLoaded(@NonNull FeatureCollection featureCollection) {
       )
     );
 
+    // debug log getters
+    SymbolLayer symbolLayer = mapboxMap.getLayerAs(LAYER_ID);
+    Timber.e("Property value for %s: %s","iconImage", symbolLayer.getIconImage().getExpression());
+    Timber.e("Property value for %s: %s","iconAllowOverlap", symbolLayer.getIconAllowOverlap().getValue());
+
     new GenerateSymbolTask(mapboxMap, this).execute(featureCollection);
   }
 

platform/android/src/style/conversion/property_value.hpp

@@ -38,7 +38,11 @@ class PropertyValueEvaluator {
     }
 
     jni::jobject* operator()(const mbgl::style::CompositeFunction<T> &value) const {
-      return *convert<jni::jobject*, mbgl::style::CompositeFunction<T>>(env, value);
+        return *convert<jni::jobject*, mbgl::style::CompositeFunction<T>>(env, value);
+    }
+
+    jni::jobject*operator()(const mbgl::style::expression::Expression &value) const {
+        return *convert<jni::jobject*, mbgl::style::expression::Expression>(env, value);
     }
 
 private: