1 files changed, 34 insertions, 0 deletions
diff --git a/Firestore/Source/Core/FSTListenSequence.m b/Firestore/Source/Core/FSTListenSequence.m
new file mode 100644
index 0000000..27ade7c
--- /dev/null
+++ b/Firestore/Source/Core/FSTListenSequence.m
@@ -0,0 +1,34 @@
+#import "FSTListenSequence.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+#pragma mark - FSTListenSequence
+
+@interface FSTListenSequence () {
+  FSTListenSequenceNumber _previousSequenceNumber;
+}
+
+@end
+
+@implementation FSTListenSequence
+
+#pragma mark - Constructors
+
+- (instancetype)initStartingAfter:(FSTListenSequenceNumber)after {
+  self = [super init];
+  if (self) {
+    _previousSequenceNumber = after;
+  }
+  return self;
+}
+
+#pragma mark - Public methods
+
+- (FSTListenSequenceNumber)next {
+  _previousSequenceNumber++;
+  return _previousSequenceNumber;
+}
+
+@end
+
+NS_ASSUME_NONNULL_END
+\ No newline at end of file