[ios, macos] Make MGLMapView.style property nullable (#7664)

* [ios, macos] Made MGLMapView.style property nullable

MGLMapView’s style property is now nullable (optional in Swift). The property is set to nil while the style loads and in the event that the style has failed to load.

* [ios, macos] Switch to delegate method

* [macos] Create MGLMapView programmatically for layer tests

When MGLMapView is created via a nib, -initWithCoder: is called, causing styleURL to be set to nil, in turn causing the default Streets style to be loaded, fooling MGLStyleLayerTests into thinking one-line has been loaded. Instead, create MGLMapView programmatically, passing the intended style URL into the initializer, preventing Streets from being loaded.

18 files changed, 99 insertions, 90 deletions

diff --git a/platform/darwin/src/MGLCircleStyleLayer.h b/platform/darwin/src/MGLCircleStyleLayer.h
index 186dfd23f6..1117077d59 100644
--- a/platform/darwin/src/MGLCircleStyleLayer.h
+++ b/platform/darwin/src/MGLCircleStyleLayer.h
@@ -72,7 +72,7 @@ typedef NS_ENUM(NSUInteger, MGLCircleTranslationAnchor) {
  ])
  layer.circleOpacity = MGLStyleValue(rawValue: 0.7)
  layer.predicate = NSPredicate(format: "%K == %@", "marital-status", "married")
- mapView.style.addLayer(layer)
+ mapView.style?.addLayer(layer)
  ```
  */
 @interface MGLCircleStyleLayer : MGLVectorStyleLayer
diff --git a/platform/darwin/src/MGLFillStyleLayer.h b/platform/darwin/src/MGLFillStyleLayer.h
index 6fae42cefe..d05b21eb51 100644
--- a/platform/darwin/src/MGLFillStyleLayer.h
+++ b/platform/darwin/src/MGLFillStyleLayer.h
@@ -45,7 +45,7 @@ typedef NS_ENUM(NSUInteger, MGLFillTranslationAnchor) {
  layer.sourceLayerIdentifier = "parks"
  layer.fillColor = MGLStyleValue(rawValue: .green)
  layer.predicate = NSPredicate(format: "type == %@", "national-park")
- mapView.style.addLayer(layer)
+ mapView.style?.addLayer(layer)
  ```
  */
 @interface MGLFillStyleLayer : MGLVectorStyleLayer
diff --git a/platform/darwin/src/MGLLineStyleLayer.h b/platform/darwin/src/MGLLineStyleLayer.h
index a9f1b4c866..9b37a97460 100644
--- a/platform/darwin/src/MGLLineStyleLayer.h
+++ b/platform/darwin/src/MGLLineStyleLayer.h
@@ -100,7 +100,7 @@ typedef NS_ENUM(NSUInteger, MGLLineTranslationAnchor) {
  layer.lineColor = MGLStyleValue(rawValue: .brown)
  layer.lineCap = MGLStyleValue(rawValue: NSValue(mglLineCap: .round))
  layer.predicate = NSPredicate(format: "%K == %@", "trail-type", "mountain-biking")
- mapView.style.addLayer(layer)
+ mapView.style?.addLayer(layer)
  ```
  */
 @interface MGLLineStyleLayer : MGLVectorStyleLayer
diff --git a/platform/darwin/src/MGLRasterSource.h b/platform/darwin/src/MGLRasterSource.h
index cd95e85c5b..c2807c8d2e 100644
--- a/platform/darwin/src/MGLRasterSource.h
+++ b/platform/darwin/src/MGLRasterSource.h
@@ -47,7 +47,7 @@ extern const MGLTileSourceOption MGLTileSourceOptionTileSize;
          MGLAttributionInfo(title: NSAttributedString(string: "© Mapbox"), url: URL(string: "http://mapbox.com"))
      ]
  ])
- mapView.style.addSource(source)
+ mapView.style?.addSource(source)
  ```
  */
 @interface MGLRasterSource : MGLTileSource
diff --git a/platform/darwin/src/MGLRasterStyleLayer.h b/platform/darwin/src/MGLRasterStyleLayer.h
index 54a3149e8c..736e8ee2f5 100644
--- a/platform/darwin/src/MGLRasterStyleLayer.h
+++ b/platform/darwin/src/MGLRasterStyleLayer.h
@@ -29,7 +29,7 @@ NS_ASSUME_NONNULL_BEGIN
  ```swift
  let layer = MGLRasterStyleLayer(identifier: "clouds", source: source)
  layer.rasterOpacity = MGLStyleValue(rawValue: 0.5)
- mapView.style.addLayer(layer)
+ mapView.style?.addLayer(layer)
  ```
  */
 @interface MGLRasterStyleLayer : MGLForegroundStyleLayer
diff --git a/platform/darwin/src/MGLShapeSource.h b/platform/darwin/src/MGLShapeSource.h
index a276864be7..8c8a2ab4e5 100644
--- a/platform/darwin/src/MGLShapeSource.h
+++ b/platform/darwin/src/MGLShapeSource.h
@@ -105,7 +105,7 @@ extern const MGLShapeSourceOption MGLShapeSourceOptionSimplificationTolerance;
  let polyline = MGLPolylineFeature(coordinates: &coordinates, count: UInt(coordinates.count))
  let shape = MGLShapeCollectionFeature(shapes: [polyline])
  let source = MGLShapeSource(identifier: "lines", shape: shape, options: nil)
- mapView.style.addSource(source)
+ mapView.style?.addSource(source)
  ```
  */
 @interface MGLShapeSource : MGLSource
diff --git a/platform/darwin/src/MGLSymbolStyleLayer.h b/platform/darwin/src/MGLSymbolStyleLayer.h
index 690624c85a..c693978ab6 100644
--- a/platform/darwin/src/MGLSymbolStyleLayer.h
+++ b/platform/darwin/src/MGLSymbolStyleLayer.h
@@ -273,7 +273,7 @@ typedef NS_ENUM(NSUInteger, MGLTextTranslationAnchor) {
  layer.textJustification = MGLStyleValue(rawValue: NSValue(mglTextJustification: .left))
  layer.textAnchor = MGLStyleValue(rawValue: NSValue(mglTextAnchor: .left))
  layer.predicate = NSPredicate(format: "%K == %@", "venue-type", "coffee")
- mapView.style.addLayer(layer)
+ mapView.style?.addLayer(layer)
  ```
  */
 @interface MGLSymbolStyleLayer : MGLVectorStyleLayer
diff --git a/platform/darwin/src/MGLVectorSource.h b/platform/darwin/src/MGLVectorSource.h
index aa867adb6c..5032ca3863 100644
--- a/platform/darwin/src/MGLVectorSource.h
+++ b/platform/darwin/src/MGLVectorSource.h
@@ -35,7 +35,7 @@ NS_ASSUME_NONNULL_BEGIN
          MGLAttributionInfo(title: NSAttributedString(string: "© Mapbox"), url: URL(string: "http://mapbox.com"))
      ]
  ])
- mapView.style.addSource(source)
+ mapView.style?.addSource(source)
  ```
  */
 @interface MGLVectorSource : MGLTileSource
diff --git a/platform/darwin/src/MGLVectorStyleLayer.h b/platform/darwin/src/MGLVectorStyleLayer.h
index d33494c3e4..360b86c517 100644
--- a/platform/darwin/src/MGLVectorStyleLayer.h
+++ b/platform/darwin/src/MGLVectorStyleLayer.h
@@ -144,7 +144,7 @@ NS_ASSUME_NONNULL_BEGIN
  let layer = MGLLineStyleLayer(identifier: "contour", source: terrain)
  layer.sourceLayerIdentifier = "contours"
  layer.predicate = NSPredicate(format: "(index == 5 || index == 10) && ele >= 1500.0")
- mapView.style.addLayer(layer)
+ mapView.style?.addLayer(layer)
  ```
  */
 @property (nonatomic, nullable) NSPredicate *predicate;
diff --git a/platform/darwin/test/MGLDocumentationExampleTests.swift b/platform/darwin/test/MGLDocumentationExampleTests.swift
index 65c145456a..5f0e83b2ca 100644
--- a/platform/darwin/test/MGLDocumentationExampleTests.swift
+++ b/platform/darwin/test/MGLDocumentationExampleTests.swift
@@ -68,10 +68,10 @@ class MGLDocumentationExampleTests: XCTestCase, MGLMapViewDelegate {
         let polyline = MGLPolylineFeature(coordinates: &coordinates, count: UInt(coordinates.count))
         let shape = MGLShapeCollectionFeature(shapes: [polyline])
         let source = MGLShapeSource(identifier: "lines", shape: shape, options: nil)
-        mapView.style.addSource(source)
+        mapView.style?.addSource(source)
         //#-end-example-code
 
-        XCTAssertNotNil(mapView.style.source(withIdentifier: "lines"))
+        XCTAssertNotNil(mapView.style?.source(withIdentifier: "lines"))
     }
 
     func testMGLRasterSource() {
@@ -84,10 +84,10 @@ class MGLDocumentationExampleTests: XCTestCase, MGLMapViewDelegate {
                 MGLAttributionInfo(title: NSAttributedString(string: "© Mapbox"), url: URL(string: "http://mapbox.com"))
             ]
         ])
-        mapView.style.addSource(source)
+        mapView.style?.addSource(source)
         //#-end-example-code
 
-        XCTAssertNotNil(mapView.style.source(withIdentifier: "clouds"))
+        XCTAssertNotNil(mapView.style?.source(withIdentifier: "clouds"))
     }
 
     func testMGLVectorSource() {
@@ -99,15 +99,15 @@ class MGLDocumentationExampleTests: XCTestCase, MGLMapViewDelegate {
                 MGLAttributionInfo(title: NSAttributedString(string: "© Mapbox"), url: URL(string: "http://mapbox.com"))
             ]
         ])
-        mapView.style.addSource(source)
+        mapView.style?.addSource(source)
         //#-end-example-code
 
-        XCTAssertNotNil(mapView.style.source(withIdentifier: "pois"))
+        XCTAssertNotNil(mapView.style?.source(withIdentifier: "pois"))
     }
 
     func testMGLCircleStyleLayer() {
         let population = MGLVectorSource(identifier: "population", configurationURL: URL(string: "https://example.com/style.json")!)
-        mapView.style.addSource(population)
+        mapView.style?.addSource(population)
         
         //#-example-code
         let layer = MGLCircleStyleLayer(identifier: "circles", source: population)
@@ -119,15 +119,15 @@ class MGLDocumentationExampleTests: XCTestCase, MGLMapViewDelegate {
         ])
         layer.circleOpacity = MGLStyleValue(rawValue: 0.7)
         layer.predicate = NSPredicate(format: "%K == %@", "marital-status", "married")
-        mapView.style.addLayer(layer)
+        mapView.style?.addLayer(layer)
         //#-end-example-code
 
-        XCTAssertNotNil(mapView.style.layer(withIdentifier: "circles"))
+        XCTAssertNotNil(mapView.style?.layer(withIdentifier: "circles"))
     }
 
     func testMGLLineStyleLayer() {
         let trails = MGLVectorSource(identifier: "trails", configurationURL: URL(string: "https://example.com/style.json")!)
-        mapView.style.addSource(trails)
+        mapView.style?.addSource(trails)
 
         //#-example-code
         let layer = MGLLineStyleLayer(identifier: "trails-path", source: trails)
@@ -139,30 +139,30 @@ class MGLDocumentationExampleTests: XCTestCase, MGLMapViewDelegate {
         layer.lineColor = MGLStyleValue(rawValue: .brown)
         layer.lineCap = MGLStyleValue(rawValue: NSValue(mglLineCap: .round))
         layer.predicate = NSPredicate(format: "%K == %@", "trail-type", "mountain-biking")
-        mapView.style.addLayer(layer)
+        mapView.style?.addLayer(layer)
         //#-end-example-code
 
-        XCTAssertNotNil(mapView.style.layer(withIdentifier: "trails-path"))
+        XCTAssertNotNil(mapView.style?.layer(withIdentifier: "trails-path"))
     }
 
     func testMGLFillStyleLayer() {
         let parks = MGLVectorSource(identifier: "parks", configurationURL: URL(string: "https://example.com/style.json")!)
-        mapView.style.addSource(parks)
+        mapView.style?.addSource(parks)
 
         //#-example-code
         let layer = MGLFillStyleLayer(identifier: "parks", source: parks)
         layer.sourceLayerIdentifier = "parks"
         layer.fillColor = MGLStyleValue(rawValue: .green)
         layer.predicate = NSPredicate(format: "type == %@", "national-park")
-        mapView.style.addLayer(layer)
+        mapView.style?.addLayer(layer)
         //#-end-example-code
 
-        XCTAssertNotNil(mapView.style.layer(withIdentifier: "parks"))
+        XCTAssertNotNil(mapView.style?.layer(withIdentifier: "parks"))
     }
 
     func testMGLSymbolStyleLayer() {
         let pois = MGLVectorSource(identifier: "pois", configurationURL: URL(string: "https://example.com/style.json")!)
-        mapView.style.addSource(pois)
+        mapView.style?.addSource(pois)
 
         //#-example-code
         let layer = MGLSymbolStyleLayer(identifier: "coffeeshops", source: pois)
@@ -179,10 +179,10 @@ class MGLDocumentationExampleTests: XCTestCase, MGLMapViewDelegate {
         layer.textJustification = MGLStyleValue(rawValue: NSValue(mglTextJustification: .left))
         layer.textAnchor = MGLStyleValue(rawValue: NSValue(mglTextAnchor: .left))
         layer.predicate = NSPredicate(format: "%K == %@", "venue-type", "coffee")
-        mapView.style.addLayer(layer)
+        mapView.style?.addLayer(layer)
         //#-end-example-code
 
-        XCTAssertNotNil(mapView.style.layer(withIdentifier: "coffeeshops"))
+        XCTAssertNotNil(mapView.style?.layer(withIdentifier: "coffeeshops"))
     }
 
     func testMGLRasterStyleLayer() {
@@ -194,28 +194,28 @@ class MGLDocumentationExampleTests: XCTestCase, MGLMapViewDelegate {
                 MGLAttributionInfo(title: NSAttributedString(string: "© Mapbox"), url: URL(string: "http://mapbox.com"))
             ]
         ])
-        mapView.style.addSource(source)
+        mapView.style?.addSource(source)
 
         //#-example-code
         let layer = MGLRasterStyleLayer(identifier: "clouds", source: source)
         layer.rasterOpacity = MGLStyleValue(rawValue: 0.5)
-        mapView.style.addLayer(layer)
+        mapView.style?.addLayer(layer)
         //#-end-example-code
 
-        XCTAssertNotNil(mapView.style.layer(withIdentifier: "clouds"))
+        XCTAssertNotNil(mapView.style?.layer(withIdentifier: "clouds"))
     }
 
     func testMGLVectorStyleLayer$predicate() {
         let terrain = MGLVectorSource(identifier: "terrain", configurationURL: URL(string: "https://example.com/style.json")!)
-        mapView.style.addSource(terrain)
+        mapView.style?.addSource(terrain)
 
         //#-example-code
         let layer = MGLLineStyleLayer(identifier: "contour", source: terrain)
         layer.sourceLayerIdentifier = "contours"
         layer.predicate = NSPredicate(format: "(index == 5 || index == 10) && ele >= 1500.0")
-        mapView.style.addLayer(layer)
+        mapView.style?.addLayer(layer)
         //#-end-example-code
 
-        XCTAssertNotNil(mapView.style.layer(withIdentifier: "contour"))
+        XCTAssertNotNil(mapView.style?.layer(withIdentifier: "contour"))
     }
 }
diff --git a/platform/darwin/test/MGLStyleLayerTests.h b/platform/darwin/test/MGLStyleLayerTests.h
index 74ce62e894..65322ff331 100644
--- a/platform/darwin/test/MGLStyleLayerTests.h
+++ b/platform/darwin/test/MGLStyleLayerTests.h
@@ -5,7 +5,6 @@
 @interface MGLStyleLayerTests : XCTestCase <MGLMapViewDelegate>
 
 @property (nonatomic) IBOutlet MGLMapView *mapView;
-@property (nonatomic) XCTestExpectation *expectation;
 @property (nonatomic, copy, readonly, class) NSString *layerType;
 
 - (void)testPropertyName:(NSString *)name isBoolean:(BOOL)isBoolean;
diff --git a/platform/darwin/test/MGLStyleLayerTests.m b/platform/darwin/test/MGLStyleLayerTests.m
index 66bdc0df0b..e9ac0794a7 100644
--- a/platform/darwin/test/MGLStyleLayerTests.m
+++ b/platform/darwin/test/MGLStyleLayerTests.m
@@ -11,18 +11,27 @@
 - (void)setUp {
     [super setUp];
     [MGLAccountManager setAccessToken:@"pk.feedcafedeadbeefbadebede"];
+    NSURL *styleURL = [[NSBundle bundleForClass:[self class]] URLForResource:@"one-liner" withExtension:@"json"];
 #if TARGET_OS_IPHONE
     UIApplication *app = [UIApplication sharedApplication];
     UIViewController *vc = [[UIViewController alloc] init];
     app.keyWindow.rootViewController = vc;
     [vc view]; // Force load xib
-    _mapView = [[MGLMapView alloc] initWithFrame:CGRectMake(0, 0, 256, 256)];
+    _mapView = [[MGLMapView alloc] initWithFrame:CGRectMake(0, 0, 256, 256) styleURL:styleURL];
     [vc.view addSubview:_mapView];
-    _mapView.delegate = self;
 #else
     NSWindowController *windowController = [[NSWindowController alloc] initWithWindowNibName:@"MGLStyleLayerTests" owner:self];
+    NSView *contentView = windowController.window.contentView;
+    _mapView = [[MGLMapView alloc] initWithFrame:contentView.bounds styleURL:styleURL];
+    [contentView addSubview:_mapView];
     [windowController showWindow:nil];
 #endif
+    _mapView.delegate = self;
+    XCTAssertNil(_mapView.style);
+    [self keyValueObservingExpectationForObject:self.mapView keyPath:@"style" handler:^BOOL(MGLMapView * _Nonnull observedMapView, NSDictionary * _Nonnull change) {
+        return observedMapView.style != nil;
+    }];
+    [self waitForExpectationsWithTimeout:1 handler:nil];
 }
 
 - (void)tearDown {
diff --git a/platform/darwin/test/MGLStyleLayerTests.xib b/platform/darwin/test/MGLStyleLayerTests.xib
index cc336191ef..d21f5753fc 100644
--- a/platform/darwin/test/MGLStyleLayerTests.xib
+++ b/platform/darwin/test/MGLStyleLayerTests.xib
@@ -1,38 +1,21 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="10117" systemVersion="16A304a" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="11762" systemVersion="15G1212" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
     <dependencies>
-        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="10117"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="11762"/>
+        <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
     </dependencies>
     <objects>
-        <customObject id="-2" userLabel="File's Owner" customClass="MGLMapViewTests">
-            <connections>
-                <outlet property="mapView" destination="6RL-d9-juy" id="0ch-aR-Um6"/>
-            </connections>
-        </customObject>
+        <customObject id="-2" userLabel="File's Owner" customClass="MGLMapViewTests"/>
         <customObject id="-1" userLabel="First Responder" customClass="FirstResponder"/>
         <customObject id="-3" userLabel="Application" customClass="NSObject"/>
         <window title="MGLMapViewTests" allowsToolTipsWhenApplicationIsInactive="NO" autorecalculatesKeyViewLoop="NO" oneShot="NO" releasedWhenClosed="NO" animationBehavior="default" id="QvC-M9-y7g">
             <windowStyleMask key="styleMask" titled="YES" closable="YES" miniaturizable="YES" resizable="YES"/>
             <windowPositionMask key="initialPositionMask" leftStrut="YES" rightStrut="YES" topStrut="YES" bottomStrut="YES"/>
             <rect key="contentRect" x="196" y="240" width="256" height="256"/>
-            <rect key="screenRect" x="0.0" y="0.0" width="1920" height="1058"/>
+            <rect key="screenRect" x="0.0" y="0.0" width="1280" height="777"/>
             <view key="contentView" wantsLayer="YES" id="EiT-Mj-1SZ">
                 <rect key="frame" x="0.0" y="0.0" width="256" height="256"/>
                 <autoresizingMask key="autoresizingMask"/>
-                <subviews>
-                    <customView translatesAutoresizingMaskIntoConstraints="NO" id="6RL-d9-juy" customClass="MGLMapView">
-                        <rect key="frame" x="0.0" y="0.0" width="256" height="256"/>
-                        <connections>
-                            <outlet property="delegate" destination="-2" id="6kS-ct-JEg"/>
-                        </connections>
-                    </customView>
-                </subviews>
-                <constraints>
-                    <constraint firstItem="6RL-d9-juy" firstAttribute="leading" secondItem="EiT-Mj-1SZ" secondAttribute="leading" id="KEN-aL-UF0"/>
-                    <constraint firstAttribute="bottom" secondItem="6RL-d9-juy" secondAttribute="bottom" id="V27-f3-xHZ"/>
-                    <constraint firstAttribute="trailing" secondItem="6RL-d9-juy" secondAttribute="trailing" id="vjq-iM-OyA"/>
-                    <constraint firstItem="6RL-d9-juy" firstAttribute="top" secondItem="EiT-Mj-1SZ" secondAttribute="top" id="yWg-v4-wJB"/>
-                </constraints>
             </view>
         </window>
     </objects>
diff --git a/platform/darwin/test/MGLStyleTests.mm b/platform/darwin/test/MGLStyleTests.mm
index bcad7ab508..b771ff0af6 100644
--- a/platform/darwin/test/MGLStyleTests.mm
+++ b/platform/darwin/test/MGLStyleTests.mm
@@ -39,7 +39,13 @@
     [super setUp];
     
     [MGLAccountManager setAccessToken:@"pk.feedcafedeadbeefbadebede"];
-    self.mapView = [[MGLMapView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
+    NSURL *styleURL = [[NSBundle bundleForClass:[self class]] URLForResource:@"one-liner" withExtension:@"json"];
+    self.mapView = [[MGLMapView alloc] initWithFrame:CGRectMake(0, 0, 100, 100) styleURL:styleURL];
+    XCTAssertNil(self.mapView.style);
+    [self keyValueObservingExpectationForObject:self.mapView keyPath:@"style" handler:^BOOL(MGLMapView * _Nonnull observedMapView, NSDictionary * _Nonnull change) {
+        return observedMapView.style != nil;
+    }];
+    [self waitForExpectationsWithTimeout:1 handler:nil];
 }
 
 - (void)tearDown {
@@ -250,12 +256,16 @@
     [self.style insertLayer:layer0 belowLayer:layer1];
     
     NSArray<MGLStyleLayer *> *layers = [self.style layers];
+    NSUInteger startIndex = 0;
+    if ([layers.firstObject.identifier isEqualToString:@"com.mapbox.annotations.points"]) {
+        startIndex++;
+    }
     
-    XCTAssert([[layers[0] identifier] isEqualToString:layer0.identifier]);
-    XCTAssert([[layers[1] identifier] isEqualToString:layer1.identifier]);
-    XCTAssert([[layers[2] identifier] isEqualToString:layer2.identifier]);
-    XCTAssert([[layers[3] identifier] isEqualToString:layer3.identifier]);
-    XCTAssert([[layers[4] identifier] isEqualToString:layer4.identifier]);
+    XCTAssertEqualObjects(layers[startIndex++].identifier, layer0.identifier);
+    XCTAssertEqualObjects(layers[startIndex++].identifier, layer1.identifier);
+    XCTAssertEqualObjects(layers[startIndex++].identifier, layer2.identifier);
+    XCTAssertEqualObjects(layers[startIndex++].identifier, layer3.identifier);
+    XCTAssertEqualObjects(layers[startIndex++].identifier, layer4.identifier);
 }
 
 @end
diff --git a/platform/ios/src/MGLMapView.h b/platform/ios/src/MGLMapView.h
index 771a48c7ff..62f053e96b 100644
--- a/platform/ios/src/MGLMapView.h
+++ b/platform/ios/src/MGLMapView.h
@@ -123,6 +123,13 @@ IB_DESIGNABLE
  Unlike the `styleURL` property, this property is set to an object that allows
  you to manipulate every aspect of the style locally.
  
+ If the style is loading, this property is set to `nil` until the style finishes
+ loading. If the style has failed to load, this property is set to `nil`.
+ Because the style loads asynchronously, you should manipulate it in the
+ `-[MGLMapViewDelegate mapView:didFinishLoadingStyle:]` or
+ `-[MGLMapViewDelegate mapViewDidFinishLoadingMap:]` method. It is not possible
+ to manipulate the style before it has finished loading.
+ 
  @note The default styles provided by Mapbox contain sources and layers with
     identifiers that will change over time. Applications that use APIs that
     manipulate a style's sources and layers must first set the style URL to an
@@ -130,7 +137,7 @@ IB_DESIGNABLE
     `+[MGLStyle outdoorsStyleURLWithVersion:]`, `MGLMapView`'s “Style URL”
     inspectable in Interface Builder, or a manually constructed `NSURL`.
  */
-@property (nonatomic, readonly) MGLStyle *style;
+@property (nonatomic, readonly, nullable) MGLStyle *style;
 
 /**
  URLs of the styles bundled with the library.
diff --git a/platform/ios/src/MGLMapView.mm b/platform/ios/src/MGLMapView.mm
index ddb11ffbb7..f8ca673093 100644
--- a/platform/ios/src/MGLMapView.mm
+++ b/platform/ios/src/MGLMapView.mm
@@ -347,6 +347,11 @@ public:
     return self;
 }
 
++ (NS_SET_OF(NSString *) *)keyPathsForValuesAffectingStyle
+{
+    return [NSSet setWithObject:@"styleURL"];
+}
+
 + (NS_SET_OF(NSString *) *)keyPathsForValuesAffectingStyleURL
 {
     return [NSSet setWithObjects:@"styleURL__", nil];
@@ -369,10 +374,8 @@ public:
     }
 
     styleURL = styleURL.mgl_URLByStandardizingScheme;
-    [self willChangeValueForKey:@"style"];
-    _style = [[MGLStyle alloc] initWithMapView:self];
+    self.style = nil;
     _mbglMap->setStyleURL([[styleURL absoluteString] UTF8String]);
-    [self didChangeValueForKey:@"style"];
 }
 
 - (IBAction)reloadStyle:(__unused id)sender {
@@ -4682,11 +4685,7 @@ public:
         }
         case mbgl::MapChangeDidFinishLoadingStyle:
         {
-            [self.style willChangeValueForKey:@"name"];
-            [self.style willChangeValueForKey:@"sources"];
-            [self.style didChangeValueForKey:@"sources"];
-            [self.style willChangeValueForKey:@"layers"];
-            [self.style didChangeValueForKey:@"layers"];
+            self.style = [[MGLStyle alloc] initWithMapView:self];
             if ([self.delegate respondsToSelector:@selector(mapView:didFinishLoadingStyle:)])
             {
                 [self.delegate mapView:self didFinishLoadingStyle:self.style];
diff --git a/platform/macos/src/MGLMapView.h b/platform/macos/src/MGLMapView.h
index ea87f3b338..954e5a2c75 100644
--- a/platform/macos/src/MGLMapView.h
+++ b/platform/macos/src/MGLMapView.h
@@ -94,6 +94,13 @@ IB_DESIGNABLE
  Unlike the `styleURL` property, this property is set to an object that allows
  you to manipulate every aspect of the style locally.
  
+ If the style is loading, this property is set to `nil` until the style finishes
+ loading. If the style has failed to load, this property is set to `nil`.
+ Because the style loads asynchronously, you should manipulate it in the
+ `-[MGLMapViewDelegate mapView:didFinishLoadingStyle:]` or
+ `-[MGLMapViewDelegate mapViewDidFinishLoadingMap:]` method. It is not possible
+ to manipulate the style before it has finished loading.
+ 
  @note The default styles provided by Mapbox contain sources and layers with
     identifiers that will change over time. Applications that use APIs that
     manipulate a style's sources and layers must first set the style URL to an
@@ -101,7 +108,7 @@ IB_DESIGNABLE
     `+[MGLStyle outdoorsStyleURLWithVersion:]`, `MGLMapView`'s “Style URL”
     inspectable in Interface Builder, or a manually constructed `NSURL`.
  */
-@property (nonatomic, readonly) MGLStyle *style;
+@property (nonatomic, readonly, nullable) MGLStyle *style;
 
 /**
  URL of the style currently displayed in the receiver.
diff --git a/platform/macos/src/MGLMapView.mm b/platform/macos/src/MGLMapView.mm
index 5c555925c4..9ed399c789 100644
--- a/platform/macos/src/MGLMapView.mm
+++ b/platform/macos/src/MGLMapView.mm
@@ -590,6 +590,10 @@ public:
 
 #pragma mark Style
 
++ (NS_SET_OF(NSString *) *)keyPathsForValuesAffectingStyle {
+    return [NSSet setWithObject:@"styleURL"];
+}
+
 - (nonnull NSURL *)styleURL {
     NSString *styleURLString = @(_mbglMap->getStyleURL().c_str()).mgl_stringOrNilIfEmpty;
     return styleURLString ? [NSURL URLWithString:styleURLString] : [MGLStyle streetsStyleURLWithVersion:MGLStyleDefaultVersion];
@@ -611,10 +615,8 @@ public:
     }
 
     styleURL = styleURL.mgl_URLByStandardizingScheme;
-    [self willChangeValueForKey:@"style"];
-    _style = [[MGLStyle alloc] initWithMapView:self];
+    self.style = nil;
     _mbglMap->setStyleURL(styleURL.absoluteString.UTF8String);
-    [self didChangeValueForKey:@"style"];
 }
 
 - (IBAction)reloadStyle:(__unused id)sender {
@@ -623,6 +625,10 @@ public:
     self.styleURL = styleURL;
 }
 
+- (mbgl::Map *)mbglMap {
+    return _mbglMap;
+}
+
 #pragma mark View hierarchy and drawing
 
 - (void)viewWillMoveToWindow:(NSWindow *)newWindow {
@@ -916,11 +922,7 @@ public:
         }
         case mbgl::MapChangeDidFinishLoadingStyle:
         {
-            [self.style willChangeValueForKey:@"name"];
-            [self.style willChangeValueForKey:@"sources"];
-            [self.style didChangeValueForKey:@"sources"];
-            [self.style willChangeValueForKey:@"layers"];
-            [self.style didChangeValueForKey:@"layers"];
+            self.style = [[MGLStyle alloc] initWithMapView:self];
             if ([self.delegate respondsToSelector:@selector(mapView:didFinishLoadingStyle:)])
             {
                 [self.delegate mapView:self didFinishLoadingStyle:self.style];
@@ -2268,13 +2270,6 @@ public:
     }
 }
 
-#pragma mark - Runtime styling
-
-- (mbgl::Map *)mbglMap
-{
-    return _mbglMap;
-}
-
 #pragma mark MGLMultiPointDelegate methods
 
 - (double)alphaForShapeAnnotation:(MGLShape *)annotation {