[ios, macos] Key-value compliance for MGLStyle

Replaced -[MGLMapView style] with a property. Keep the MGLStyle object around for the lifetime of the style. Bracket changes to layers in will/did change calls.

platform/darwin/src/MGLStyle.mm

@@ -32,8 +32,10 @@
 #include <mbgl/style/sources/raster_source.hpp>
 #include <mbgl/mbgl.hpp>
 
-@interface MGLStyle()
-@property (nonatomic, weak) MGLMapView *mapView;
+@interface MGLStyle ()
+
+@property (nonatomic, readwrite, weak) MGLMapView *mapView;
+
 @end
 
 @implementation MGLStyle
@@ -90,6 +92,15 @@ + (NSURL *)emeraldStyleURL {
     return MGLStyleURL_emerald;
 }
 
+#pragma mark -
+
+- (instancetype)initWithMapView:(MGLMapView *)mapView {
+    if (self = [super init]) {
+        _mapView = mapView;
+    }
+    return self;
+}
+
 #pragma mark Sources
 
 - (mbgl::style::Source *)mbglSourceWithIdentifier:(NSString *)identifier
@@ -252,19 +263,25 @@ - (Class)classFromLayer:(mbgl::style::Layer *)layer
 
 - (void)removeLayer:(id <MGLStyleLayer_Private>)styleLayer
 {
+    [self willChangeValueForKey:@"layers"];
     self.mapView.mbglMap->removeLayer(styleLayer.layer->getID());
+    [self didChangeValueForKey:@"layers"];
 }
 
 - (void)addLayer:(id <MGLStyleLayer, MGLStyleLayer_Private>)styleLayer
 {
+    [self willChangeValueForKey:@"layers"];
     self.mapView.mbglMap->addLayer(std::unique_ptr<mbgl::style::Layer>(styleLayer.layer));
+    [self didChangeValueForKey:@"layers"];
 }
 
 - (void)insertLayer:(id <MGLStyleLayer, MGLStyleLayer_Private>)styleLayer
          belowLayer:(id <MGLStyleLayer, MGLStyleLayer_Private>)belowLayer
 {
+    [self willChangeValueForKey:@"layers"];
     const mbgl::optional<std::string> belowLayerId{[belowLayer layerIdentifier].UTF8String};
     self.mapView.mbglMap->addLayer(std::unique_ptr<mbgl::style::Layer>(styleLayer.layer), belowLayerId);
+    [self didChangeValueForKey:@"layers"];
 }
 
 #pragma mark Style classes

platform/darwin/src/MGLStyle_Private.h

@@ -6,7 +6,10 @@
 #include <mbgl/mbgl.hpp>
 
 @interface MGLStyle (Private)
-@property (nonatomic, weak) MGLMapView *mapView;
+
+- (instancetype)initWithMapView:(MGLMapView *)mapView;
+
+@property (nonatomic, readonly, weak) MGLMapView *mapView;
 
 - (void)setStyleClasses:(NS_ARRAY_OF(NSString *) *)appliedClasses transitionDuration:(NSTimeInterval)transitionDuration;
 

platform/ios/src/MGLMapView.h

@@ -136,6 +136,14 @@ IB_DESIGNABLE
 
 #pragma mark Configuring the Map’s Appearance
 
+/**
+ The style currently displayed in the receiver.
+ 
+ Unlike the `styleURL` property, this property is set to an object that allows
+ you to manipulate every aspect of the style locally.
+ */
+@property (nonatomic, readonly) MGLStyle *style;
+
 /**
  URLs of the styles bundled with the library.
  
@@ -153,6 +161,9 @@ IB_DESIGNABLE
  
  If you set this property to `nil`, the receiver will use the default style
  and this property will automatically be set to that style’s URL.
+ 
+ If you want to modify the current style without replacing it outright, or if
+ you want to introspect individual style attributes, use the `style` property.
  */
 @property (nonatomic, null_resettable) NSURL *styleURL;
 
@@ -1068,10 +1079,6 @@ IB_DESIGNABLE
  */
 - (void)removeOverlays:(NS_ARRAY_OF(id <MGLOverlay>) *)overlays;
 
-#pragma mark - Runtime styling API
-
-- (MGLStyle *)style;
-
 #pragma mark Accessing the Underlying Map Data
 
 /**

platform/ios/src/MGLMapView.mm

@@ -223,6 +223,9 @@ @interface MGLMapView () <UIGestureRecognizerDelegate,
 @property (nonatomic, readwrite) UIButton *attributionButton;
 @property (nonatomic) NS_MUTABLE_ARRAY_OF(NSLayoutConstraint *) *attributionButtonConstraints;
 @property (nonatomic) UIActionSheet *attributionSheet;
+
+@property (nonatomic, readwrite) MGLStyle *style;
+
 @property (nonatomic) UIPanGestureRecognizer *pan;
 @property (nonatomic) UIPinchGestureRecognizer *pinch;
 @property (nonatomic) UIRotationGestureRecognizer *rotate;
@@ -347,6 +350,7 @@ - (void)setStyleURL:(nullable NSURL *)styleURL
 
     styleURL = styleURL.mgl_URLByStandardizingScheme;
     _mbglMap->setStyleURL([[styleURL absoluteString] UTF8String]);
+    self.style = [[MGLStyle alloc] initWithMapView:self];
 }
 
 - (IBAction)reloadStyle:(__unused id)sender {
@@ -598,13 +602,6 @@ - (UIImage *)compassImage
     return image;
 }
 
-- (MGLStyle *)style
-{
-    MGLStyle *style = [[MGLStyle alloc] init];
-    style.mapView = self;
-    return style;
-}
-
 - (void)reachabilityChanged:(NSNotification *)notification
 {
     MGLReachability *reachability = [notification object];
@@ -4480,6 +4477,7 @@ - (void)notifyMapChange:(mbgl::MapChange)change
         }
         case mbgl::MapChangeWillStartLoadingMap:
         {
+            [self.style willChangeValueForKey:@"layers"];
             if ([self.delegate respondsToSelector:@selector(mapViewWillStartLoadingMap:)])
             {
                 [self.delegate mapViewWillStartLoadingMap:self];
@@ -4488,6 +4486,7 @@ - (void)notifyMapChange:(mbgl::MapChange)change
         }
         case mbgl::MapChangeDidFinishLoadingMap:
         {
+            [self.style didChangeValueForKey:@"layers"];
             if ([self.delegate respondsToSelector:@selector(mapViewDidFinishLoadingMap:)])
             {
                 [self.delegate mapViewDidFinishLoadingMap:self];

platform/macos/src/MGLMapView.h

@@ -121,6 +121,14 @@ IB_DESIGNABLE
 
 #pragma mark Configuring the Map’s Appearance
 
+/**
+ The style currently displayed in the receiver.
+ 
+ Unlike the `styleURL` property, this property is set to an object that allows
+ you to manipulate every aspect of the style locally.
+ */
+@property (nonatomic, readonly) MGLStyle *style;
+
 /**
  URL of the style currently displayed in the receiver.
  
@@ -130,6 +138,9 @@ IB_DESIGNABLE
  
  If you set this property to `nil`, the receiver will use the default style and
  this property will automatically be set to that style’s URL.
+ 
+ If you want to modify the current style without replacing it outright, or if
+ you want to introspect individual style attributes, use the `style` property.
  */
 @property (nonatomic, null_resettable) NSURL *styleURL;
 
@@ -938,10 +949,6 @@ IB_DESIGNABLE
  */
 @property (nonatomic) MGLMapDebugMaskOptions debugMask;
 
-#pragma mark Runtime styling API
-
-- (MGLStyle *)style;
-
 @end
 
 NS_ASSUME_NONNULL_END

platform/macos/src/MGLMapView.mm

@@ -137,6 +137,8 @@ @interface MGLMapView () <NSPopoverDelegate, MGLMultiPointDelegate>
 @property (nonatomic, readwrite) NSImageView *logoView;
 @property (nonatomic, readwrite) NSView *attributionView;
 
+@property (nonatomic, readwrite) MGLStyle *style;
+
 /// Mapping from reusable identifiers to annotation images.
 @property (nonatomic) NS_MUTABLE_DICTIONARY_OF(NSString *, MGLAnnotationImage *) *annotationImagesByIdentifier;
 /// Currently shown popover representing the selected annotation.
@@ -542,6 +544,7 @@ - (void)setStyleURL:(nullable NSURL *)styleURL {
 
     styleURL = styleURL.mgl_URLByStandardizingScheme;
     _mbglMap->setStyleURL(styleURL.absoluteString.UTF8String);
+    self.style = [[MGLStyle alloc] initWithMapView:self];
 }
 
 - (IBAction)reloadStyle:(__unused id)sender {
@@ -793,13 +796,15 @@ - (void)notifyMapChange:(mbgl::MapChange)change {
         }
         case mbgl::MapChangeWillStartLoadingMap:
         {
+            [self.style willChangeValueForKey:@"layers"];
             if ([self.delegate respondsToSelector:@selector(mapViewWillStartLoadingMap:)]) {
                 [self.delegate mapViewWillStartLoadingMap:self];
             }
             break;
         }
         case mbgl::MapChangeDidFinishLoadingMap:
         {
+            [self.style didChangeValueForKey:@"layers"];
             if ([self.delegate respondsToSelector:@selector(mapViewDidFinishLoadingMap:)]) {
                 [self.delegate mapViewDidFinishLoadingMap:self];
             }
@@ -2117,13 +2122,6 @@ - (void)updateAnnotationCallouts {
 
 #pragma mark - Runtime styling
 
-- (MGLStyle *)style
-{
-    MGLStyle *style = [[MGLStyle alloc] init];
-    style.mapView = self;
-    return style;
-}
-
 - (mbgl::Map *)mbglMap
 {
     return _mbglMap;