RCTAllocatedRootViewTag was moved to RCTUIManagerUtils

Summary: This logic was decoupled from RCTRootView to make it reusable.

Reviewed By: javache

Differential Revision: D6214785

fbshipit-source-id: e7419be03ba0e20d95b47c11e41789636aa6e916

React/Base/RCTRootView.m

@@ -24,6 +24,7 @@
 #import "RCTRootContentView.h"
 #import "RCTTouchHandler.h"
 #import "RCTUIManager.h"
+#import "RCTUIManagerUtils.h"
 #import "RCTUtils.h"
 #import "RCTView.h"
 #import "UIView+React.h"
@@ -243,7 +244,7 @@ - (NSNumber *)reactTag
      * NOTE: Since the bridge persists, the RootViews might be reused, so the
      * react tag must be re-assigned every time a new UIManager is created.
      */
-    self.reactTag = [_bridge.uiManager allocateRootTag];
+    self.reactTag = RCTAllocateRootViewTag();
   }
   return super.reactTag;
 }
@@ -396,14 +397,3 @@ - (CGSize)intrinsicSize
 }
 
 @end
-
-@implementation RCTUIManager (RCTRootView)
-
-- (NSNumber *)allocateRootTag
-{
-  NSNumber *rootTag = objc_getAssociatedObject(self, _cmd) ?: @1;
-  objc_setAssociatedObject(self, _cmd, @(rootTag.integerValue + 10), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
-  return rootTag;
-}
-
-@end

React/Modules/RCTUIManagerUtils.h

@@ -7,7 +7,7 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  */
 
-#import <UIKit/UIKit.h>
+#import <Foundation/Foundation.h>
 
 #import <React/RCTAssert.h>
 #import <React/RCTDefines.h>
@@ -99,3 +99,8 @@ RCT_EXTERN void RCTUnsafeExecuteOnUIManagerQueueSync(dispatch_block_t block);
  */
 #define RCTAssertUIManagerQueue() RCTAssert(RCTIsUIManagerQueue() || RCTIsPseudoUIManagerQueue(), \
 @"This function must be called on the UIManager queue")
+
+/**
+ * Returns new unique root view tag.
+ */
+RCT_EXTERN NSNumber *RCTAllocateRootViewTag(void);

React/Modules/RCTUIManagerUtils.m

@@ -9,6 +9,8 @@
 
 #import "RCTUIManagerUtils.h"
 
+#import <libkern/OSAtomic.h>
+
 #import "RCTAssert.h"
 
 char *const RCTUIManagerQueueName = "com.facebook.react.ShadowQueue";
@@ -93,3 +95,10 @@ void RCTUnsafeExecuteOnUIManagerQueueSync(dispatch_block_t block)
     }
   }
 }
+
+NSNumber *RCTAllocateRootViewTag()
+{
+  // Numbering of these tags goes from 1, 11, 21, 31, ..., 100501, ...
+  static int64_t rootViewTagCounter = -1;
+  return @(OSAtomicIncrement64(&rootViewTagCounter) * 10 + 1);
+}