Observe access token changes

The singleton `MGLAccountManager` wants to be the sole arbiter of the access token, but each instance of `mbgl::Map` (`mbgl::DefaultFileSource` in #1607) has its own copy of the access token. Now `MGLMapView` observes for changes to the `MGLAccountManager`’s access token and synchronizes `mbgl::Map` with it.

3 files changed, 29 insertions, 5 deletions

diff --git a/platform/ios/MGLAccountManager.m b/platform/ios/MGLAccountManager.m
index 97d7e5e5ec..38ef1f4ca9 100644
--- a/platform/ios/MGLAccountManager.m
+++ b/platform/ios/MGLAccountManager.m
@@ -1,6 +1,6 @@
 #import <Foundation/Foundation.h>
 
-#import "MGLAccountManager.h"
+#import "MGLAccountManager_Private.h"
 #import "MGLMapboxEvents_Private.h"
 #import "NSProcessInfo+MGLAdditions.h"
 
diff --git a/platform/ios/MGLAccountManager_Private.h b/platform/ios/MGLAccountManager_Private.h
new file mode 100644
index 0000000000..3cc05b09f0
--- /dev/null
+++ b/platform/ios/MGLAccountManager_Private.h
@@ -0,0 +1,10 @@
+#import "MGLAccountManager.h"
+
+@interface MGLAccountManager (Private)
+
+/** Returns the shared instance of the `MGLAccountManager` class. */
++ (instancetype)sharedManager;
+
+@property (atomic) NSString *accessToken;
+
+@end
diff --git a/platform/ios/MGLMapView.mm b/platform/ios/MGLMapView.mm
index cb89c58d46..997d5734aa 100644
--- a/platform/ios/MGLMapView.mm
+++ b/platform/ios/MGLMapView.mm
@@ -20,7 +20,7 @@
 #import "NSString+MGLAdditions.h"
 #import "NSProcessInfo+MGLAdditions.h"
 #import "NSException+MGLAdditions.h"
-#import "MGLAccountManager.h"
+#import "MGLAccountManager_Private.h"
 #import "MGLAnnotation.h"
 #import "MGLUserLocationAnnotationView.h"
 #import "MGLUserLocation_Private.h"
@@ -266,9 +266,12 @@ std::chrono::steady_clock::duration secondsAsDuration(float duration)
     }
     _mbglMap->resize(self.bounds.size.width, self.bounds.size.height, _glView.contentScaleFactor);
 
-    // mbgl::Map keeps its own copy of the access token.
-    NSString *accessToken = [MGLAccountManager accessToken];
-    _mbglMap->setAccessToken(accessToken ? (std::string)[accessToken UTF8String] : "");
+    // Observe for changes to the global access token (and find out the current one).
+    [[MGLAccountManager sharedManager] addObserver:self
+                                        forKeyPath:@"accessToken"
+                                           options:(NSKeyValueObservingOptionInitial |
+                                                    NSKeyValueObservingOptionNew)
+                                           context:NULL];
 
     // Notify map object when network reachability status changes.
     [[NSNotificationCenter defaultCenter] addObserver:self
@@ -410,6 +413,7 @@ std::chrono::steady_clock::duration secondsAsDuration(float duration)
     [_regionChangeDelegateQueue cancelAllOperations];
 
     [[NSNotificationCenter defaultCenter] removeObserver:self];
+    [[MGLAccountManager sharedManager] removeObserver:self forKeyPath:@"accessToken"];
 
     if (_mbglMap)
     {
@@ -1292,6 +1296,16 @@ std::chrono::steady_clock::duration secondsAsDuration(float duration)
 
 #pragma mark - Properties -
 
+- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(__unused void *)context
+{
+    // Synchronize mbgl::Map’s access token with the global one in MGLAccountManager.
+    if ([keyPath isEqualToString:@"accessToken"] && object == [MGLAccountManager sharedManager])
+    {
+        NSString *accessToken = change[NSKeyValueChangeNewKey];
+        _mbglMap->setAccessToken(accessToken ? (std::string)[accessToken UTF8String] : "");
+    }
+}
+
 + (NSSet *)keyPathsForValuesAffectingZoomEnabled
 {
     return [NSSet setWithObject:@"allowsZooming"];