Add comments for map function
diff --git a/src/objective-c/RxLibrary/GRXImmediateSingleWriter.m b/src/objective-c/RxLibrary/GRXImmediateSingleWriter.m
index a0d3b77..a3e9cd6 100644
--- a/src/objective-c/RxLibrary/GRXImmediateSingleWriter.m
+++ b/src/objective-c/RxLibrary/GRXImmediateSingleWriter.m
@@ -75,7 +75,11 @@
return;
}
+// Overrides [requestWriter(Transformations):map:] for Protocol Buffers
+// encoding.
- (GRXWriter *)map:(id (^)(id))map {
+ // Since _value is available when creating the object, we can simply
+ // apply the map and store the output.
_value = map(_value);
return self;
}