[darwin] Simplify MGLStyleLayer initialization and pointer management

Similarly to the previous commit, introduce `-[MGLStyleLayer initWithPendingLayer:]`, allowing the base class to track the owned `_pendingSource` pointer and implement `-addToMapView:` and `-removeFromMapView:` without any casts.

Fixes an issue where `-[MGLStyle layerFromMBGLLayer:]` would wind up creating layers whose `_rawLayer` and `_pendingLayer` held different values.

1 files changed, 29 insertions, 0 deletions

diff --git a/platform/darwin/src/MGLForegroundStyleLayer.mm b/platform/darwin/src/MGLForegroundStyleLayer.mm
new file mode 100644
index 0000000000..6926dfac1f
--- /dev/null
+++ b/platform/darwin/src/MGLForegroundStyleLayer.mm
@@ -0,0 +1,29 @@
+#import "MGLForegroundStyleLayer.h"
+#import "MGLForegroundStyleLayer_Private.h"
+#import "MGLStyleLayer_Private.h"
+#import "MGLSource.h"
+
+@implementation MGLForegroundStyleLayer
+
+- (instancetype)initWithRawLayer:(mbgl::style::Layer *)rawLayer source:(MGLSource *)source {
+    if (self = [super initWithRawLayer:rawLayer]) {
+        _sourceIdentifier = source.identifier;
+    }
+    return self;
+}
+
+- (instancetype)initWithPendingLayer:(std::unique_ptr<mbgl::style::Layer>)pendingLayer source:(MGLSource *)source {
+    if (self = [super initWithPendingLayer:std::move(pendingLayer)]) {
+        _sourceIdentifier = source.identifier;
+    }
+    return self;
+}
+
+- (NSString *)description {
+    return [NSString stringWithFormat:
+            @"<%@: %p; identifier = %@; sourceIdentifier = %@; visible = %@>",
+            NSStringFromClass([self class]), (void *)self, self.identifier,
+            self.sourceIdentifier, self.visible ? @"YES" : @"NO"];
+}
+
+@end