Respond to CR.

// FREEBIE

Signal/src/ViewControllers/OWSLinkDeviceViewController.m

@@ -147,7 +147,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)provisionWithParser:(OWSDeviceProvisioningURLParser *)parser
 {
     // Optimistically set this flag.
-    [OWSDevice setMayHaveLinkedDevices:YES dbConnection:self.dbConnection];
+    [OWSDeviceManager.sharedManager setMayHaveLinkedDevices:YES dbConnection:self.dbConnection];
 
     ECKeyPair *_Nullable identityKeyPair = [[OWSIdentityManager sharedManager] identityKeyPair];
     OWSAssert(identityKeyPair);

SignalServiceKit/src/Devices/OWSDevice.h

@@ -9,6 +9,19 @@ NS_ASSUME_NONNULL_BEGIN
 
 extern uint32_t const OWSDevicePrimaryDeviceId;
 
+@interface OWSDeviceManager : NSObject
+
+- (instancetype)init NS_UNAVAILABLE;
+
++ (instancetype)sharedManager;
+
+- (BOOL)mayHaveLinkedDevices:(YapDatabaseConnection *)dbConnection;
+- (void)setMayHaveLinkedDevices:(BOOL)value dbConnection:(YapDatabaseConnection *)dbConnection;
+
+@end
+
+#pragma mark -
+
 @interface OWSDevice : TSYapDatabaseObject <MTLJSONSerializing>
 
 @property (nonatomic, readonly) NSInteger deviceId;
@@ -52,11 +65,6 @@ extern uint32_t const OWSDevicePrimaryDeviceId;
  */
 - (BOOL)updateAttributesWithDevice:(OWSDevice *)other;
 
-#pragma mark - "May Have Linked Devices" Flag
-
-+ (BOOL)mayHaveLinkedDevices:(YapDatabaseConnection *)dbConnection;
-+ (void)setMayHaveLinkedDevices:(BOOL)value dbConnection:(YapDatabaseConnection *)dbConnection;
-
 @end
 
 NS_ASSUME_NONNULL_END

SignalServiceKit/src/Devices/OWSDevice.m

@@ -16,6 +16,67 @@ uint32_t const OWSDevicePrimaryDeviceId = 1;
 NSString *const kTSStorageManager_OWSDeviceCollection = @"kTSStorageManager_OWSDeviceCollection";
 NSString *const kTSStorageManager_MayHaveLinkedDevices = @"kTSStorageManager_MayHaveLinkedDevices";
 
+@interface OWSDeviceManager ()
+
+@property (atomic, nullable) NSNumber *mayHaveLinkedDevicesCached;
+
+@end
+
+#pragma mark -
+
+@implementation OWSDeviceManager
+
++ (instancetype)sharedManager
+{
+    static OWSDeviceManager *instance = nil;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        instance = [[self alloc] initDefault];
+    });
+    return instance;
+}
+
+- (instancetype)initDefault
+{
+    return [super init];
+}
+
+- (BOOL)mayHaveLinkedDevices:(YapDatabaseConnection *)dbConnection
+{
+    OWSAssert(dbConnection);
+
+    @synchronized(self)
+    {
+        if (!self.mayHaveLinkedDevicesCached) {
+            self.mayHaveLinkedDevicesCached = @([dbConnection boolForKey:kTSStorageManager_MayHaveLinkedDevices
+                                                            inCollection:kTSStorageManager_OWSDeviceCollection
+                                                            defaultValue:YES]);
+        }
+
+        return [self.mayHaveLinkedDevicesCached boolValue];
+    }
+}
+
+- (void)setMayHaveLinkedDevices:(BOOL)value dbConnection:(YapDatabaseConnection *)dbConnection
+{
+    OWSAssert(dbConnection);
+
+    @synchronized(self)
+    {
+        self.mayHaveLinkedDevicesCached = @(YES);
+
+        [dbConnection asyncReadWriteWithBlock:^(YapDatabaseReadWriteTransaction *_Nonnull transaction) {
+            [transaction setObject:@(value)
+                            forKey:kTSStorageManager_MayHaveLinkedDevices
+                      inCollection:kTSStorageManager_OWSDeviceCollection];
+        }];
+    }
+}
+
+@end
+
+#pragma mark -
+
 @interface OWSDevice ()
 
 @property (nonatomic) NSInteger deviceId;
@@ -182,26 +243,6 @@ NSString *const kTSStorageManager_MayHaveLinkedDevices = @"kTSStorageManager_May
     return self.deviceId == device.deviceId;
 }
 
-#pragma mark - "May Have Linked Devices" Flag
-
-+ (BOOL)mayHaveLinkedDevices:(YapDatabaseConnection *)dbConnection
-{
-    OWSAssert(dbConnection);
-
-    return [dbConnection boolForKey:kTSStorageManager_MayHaveLinkedDevices
-                       inCollection:kTSStorageManager_OWSDeviceCollection
-                       defaultValue:YES];
-}
-
-+ (void)setMayHaveLinkedDevices:(BOOL)value dbConnection:(YapDatabaseConnection *)dbConnection
-{
-    OWSAssert(dbConnection);
-
-    [dbConnection setBool:value
-                   forKey:kTSStorageManager_MayHaveLinkedDevices
-             inCollection:kTSStorageManager_OWSDeviceCollection];
-}
-
 @end
 
 NS_ASSUME_NONNULL_END

SignalServiceKit/src/Messages/OWSMessageSender.m

@@ -971,7 +971,7 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
         // devices, then can safely skip sending sync message.
 
         // 1. Check OWSDevice's state.
-        BOOL mayHaveLinkedDevices = [OWSDevice mayHaveLinkedDevices:self.dbConnection];
+        BOOL mayHaveLinkedDevices = [OWSDeviceManager.sharedManager mayHaveLinkedDevices:self.dbConnection];
 
         // 2. Check SignalRecipient's state.
         BOOL hasDeviceMessages = deviceMessages.count > 0;
@@ -1113,7 +1113,7 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
     if (missingDevices.count > 0) {
         NSString *localNumber = [TSAccountManager localNumber];
         if ([localNumber isEqualToString:recipient.uniqueId]) {
-            [OWSDevice setMayHaveLinkedDevices:YES dbConnection:self.dbConnection];
+            [OWSDeviceManager.sharedManager setMayHaveLinkedDevices:YES dbConnection:self.dbConnection];
         }
     }
 

SignalServiceKit/src/Storage/YapDatabaseConnection+OWS.m

@@ -57,8 +57,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (BOOL)boolForKey:(NSString *)key inCollection:(NSString *)collection defaultValue:(BOOL)defaultValue
 {
-    NSNumber *_Nullable number = [self objectForKey:key inCollection:collection ofExpectedType:[NSNumber class]];
-    return [number boolValue];
+    NSNumber *_Nullable value = [self objectForKey:key inCollection:collection ofExpectedType:[NSNumber class]];
+    return value ? [value boolValue] : defaultValue;
 }
 
 - (nullable NSData *)dataForKey:(NSString *)key inCollection:(NSString *)collection