[ios, macos] Fix layer/source typo and add more docs to macos

platform/darwin/src/MGLStyle.h

@@ -264,8 +264,8 @@ static const NSInteger MGLStyleDefaultVersion = 9;
     style URL to an explicitly versioned style using a convenience method like
     `+[MGLStyle outdoorsStyleURLWithVersion:]`, `MGLMapView`'s “Style URL”
     inspectable in Interface Builder, or a manually constructed `NSURL`. This
-    approach also avoids layer identifer name changes that will occur in the default
-    style’s layers over time.
+    approach also avoids source identifer name changes that will occur in the default
+    style’s sources over time.
  
  @param source The source to remove.
  */

platform/macos/src/MGLMapView.h

@@ -782,6 +782,14 @@ IB_DESIGNABLE
  To find out the layer names in a particular style, view the style in
  <a href="https://www.mapbox.com/studio/">Mapbox Studio</a>.
  
+ @note Layer identifiers are not guaranteed to exist across styles or different
+    versions of the same style. Applications that use this API must first set the
+    style URL to an explicitly versioned style using a convenience method like
+    `+[MGLStyle outdoorsStyleURLWithVersion:]`, `MGLMapView`'s “Style URL”
+    inspectable in Interface Builder, or a manually constructed `NSURL`. This
+    approach also avoids layer identifer name changes that will occur in the default
+    style’s layers over time.
+
  @param point A point expressed in the map view’s coordinate system.
  @param styleLayerIdentifiers A set of strings that correspond to the names of
     layers defined in the current style. Only the features contained in these
@@ -845,6 +853,14 @@ IB_DESIGNABLE
  To find out the layer names in a particular style, view the style in
  <a href="https://www.mapbox.com/studio/">Mapbox Studio</a>.
  
+ @note Layer identifiers are not guaranteed to exist across styles or different
+    versions of the same style. Applications that use this API must first set the
+    style URL to an explicitly versioned style using a convenience method like
+    `+[MGLStyle outdoorsStyleURLWithVersion:]`, `MGLMapView`'s “Style URL”
+    inspectable in Interface Builder, or a manually constructed `NSURL`. This
+    approach also avoids layer identifer name changes that will occur in the default
+    style’s layers over time.
+
  @param rect A rectangle expressed in the map view’s coordinate system.
  @param styleLayerIdentifiers A set of strings that correspond to the names of
     layers defined in the current style. Only the features contained in these
@@ -928,6 +944,20 @@ IB_DESIGNABLE
 
 #pragma mark Runtime styling API
 
+/**
+ Returns an instance of `MGLStyle` for the current map style.
+
+ The returned object is a proxy for the current map style for customization
+ purposes. It also has a set of convenience methods for creating style URLs of
+ default styles provided by Mapbox.
+
+ @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
+    explicitly versioned style using a convenience method like
+    `+[MGLStyle outdoorsStyleURLWithVersion:]`, `MGLMapView`'s “Style URL”
+    inspectable in Interface Builder, or a manually constructed `NSURL`.
+ */
 - (MGLStyle *)style;
 
 @end