Adds support to ios for the google maps styling customMapStyle prop (react-native-maps#817)

Author: ali-alamine

components/MapView.js

@@ -400,16 +400,26 @@ class MapView extends React.Component {
     }
   }
 
+  componentDidMount() {
+    const { isReady } = this.state;
+    if (isReady) {
+      this._updateStyle();
+    }
+  }
+
+  _updateStyle() {
+    const { customMapStyle } = this.props;
+    this.map.setNativeProps({ customMapStyleString: JSON.stringify(customMapStyle) });
+  }
+
   _onMapReady() {
-    const { region, initialRegion, customMapStyle } = this.props;
+    const { region, initialRegion } = this.props;
     if (region) {
       this.map.setNativeProps({ region });
     } else if (initialRegion) {
       this.map.setNativeProps({ region: initialRegion });
     }
-    if (customMapStyle) {
-      this.map.setNativeProps({ customMapStyleString: JSON.stringify(customMapStyle) });
-    }
+    this._updateStyle();
     this.setState({ isReady: true });
   }
 

ios/AirGoogleMaps/AIRGoogleMap.h

@@ -17,6 +17,7 @@
 // TODO: don't use MK region?
 @property (nonatomic, assign) MKCoordinateRegion initialRegion;
 @property (nonatomic, assign) MKCoordinateRegion region;
+@property (nonatomic, assign) NSString *customMapStyleString;
 @property (nonatomic, copy) RCTBubblingEventBlock onPress;
 @property (nonatomic, copy) RCTBubblingEventBlock onLongPress;
 @property (nonatomic, copy) RCTBubblingEventBlock onMarkerPress;

ios/AirGoogleMaps/AIRGoogleMap.m

@@ -238,6 +238,18 @@ - (void)setShowsCompass:(BOOL)showsCompass {
   self.settings.compassButton = showsCompass;
 }
 
+- (void)setCustomMapStyleString:(NSString *)customMapStyleString {
+  NSError *error;
+
+  GMSMapStyle *style = [GMSMapStyle styleWithJSONString:customMapStyleString error:&error];
+
+  if (!style) {
+    NSLog(@"The style definition could not be loaded: %@", error);
+  }
+
+  self.mapStyle = style;
+}
+
 - (BOOL)showsCompass {
   return self.settings.compassButton;
 }

ios/AirGoogleMaps/AIRGoogleMapManager.m

@@ -56,6 +56,7 @@ - (UIView *)view
 RCT_EXPORT_VIEW_PROPERTY(scrollEnabled, BOOL)
 RCT_EXPORT_VIEW_PROPERTY(pitchEnabled, BOOL)
 RCT_EXPORT_VIEW_PROPERTY(showsUserLocation, BOOL)
+RCT_EXPORT_VIEW_PROPERTY(customMapStyleString, NSString)
 RCT_EXPORT_VIEW_PROPERTY(onPress, RCTBubblingEventBlock)
 RCT_EXPORT_VIEW_PROPERTY(onLongPress, RCTBubblingEventBlock)
 RCT_EXPORT_VIEW_PROPERTY(onChange, RCTBubblingEventBlock)