fix dispatch-thread pattern

 1. Always bail early if in IB.
 2. Always run on main thread if not already.
 3. THEN dispatch_once to create the static instance.

2 files changed, 32 insertions, 33 deletions

diff --git a/platform/ios/MGLAccountManager.m b/platform/ios/MGLAccountManager.m
index 9490e91bae..32540e4e46 100644
--- a/platform/ios/MGLAccountManager.m
+++ b/platform/ios/MGLAccountManager.m
@@ -14,28 +14,28 @@
 
 @implementation MGLAccountManager
 
-static MGLAccountManager *_sharedManager;
-
 // Can be called from any thread.
 //
 + (instancetype) sharedManager {
+    if (NSProcessInfo.processInfo.mgl_isInterfaceBuilderDesignablesAgent) {
+        return;
+    }
     static dispatch_once_t onceToken;
-    dispatch_once(&onceToken, ^{
-        if ( ! NSProcessInfo.processInfo.mgl_isInterfaceBuilderDesignablesAgent) {
-            void (^setupBlock)() = ^{
-                _sharedManager = [[self alloc] init];
-                _sharedManager.mapboxMetricsEnabledSettingShownInApp = NO;
-            };
-            if ( ! [[NSThread currentThread] isMainThread]) {
-                dispatch_sync(dispatch_get_main_queue(), ^{
-                    setupBlock();
-                });
-            }
-            else {
-                setupBlock();
-            }
-        }
-    });
+    static MGLAccountManager *_sharedManager;
+    void (^setupBlock)() = ^{
+        dispatch_once(&onceToken, ^{
+            _sharedManager = [[self alloc] init];
+            _sharedManager.mapboxMetricsEnabledSettingShownInApp = NO;
+        });
+    };
+    if ( ! [[NSThread currentThread] isMainThread]) {
+        dispatch_sync(dispatch_get_main_queue(), ^{
+            setupBlock();
+        });
+    }
+    else {
+        setupBlock();
+    }
     return _sharedManager;
 }
 
diff --git a/platform/ios/MGLMapboxEvents.m b/platform/ios/MGLMapboxEvents.m
index fb94479723..9fcfc71536 100644
--- a/platform/ios/MGLMapboxEvents.m
+++ b/platform/ios/MGLMapboxEvents.m
@@ -279,25 +279,24 @@ const NSTimeInterval MGLFlushInterval = 60;
 // public class convenience methods. May return nil if this feature is disabled.
 //
 + (instancetype)sharedManager {
+    if (NSProcessInfo.processInfo.mgl_isInterfaceBuilderDesignablesAgent) {
+        return;
+    }
     static dispatch_once_t onceToken;
     static MGLMapboxEvents *_sharedManager;
-    dispatch_once(&onceToken, ^{
-        if (NSProcessInfo.processInfo.mgl_isInterfaceBuilderDesignablesAgent) {
-            return;
-        }
-        
-        void (^setupBlock)() = ^{
+    void (^setupBlock)() = ^{
+        dispatch_once(&onceToken, ^{
             _sharedManager = [[self alloc] init];
-        };
-        if ( ! [[NSThread currentThread] isMainThread]) {
-            dispatch_sync(dispatch_get_main_queue(), ^{
-                setupBlock();
-            });
-        }
-        else {
+        });
+    };
+    if ( ! [[NSThread currentThread] isMainThread]) {
+        dispatch_sync(dispatch_get_main_queue(), ^{
             setupBlock();
-        }
-    });
+        });
+    }
+    else {
+        setupBlock();
+    }
     return _sharedManager;
 }