Lazily instantiate native modules

Summary: Instead of sending a list of modules over to JS on startup (and actually blocking script execution) instead provide a proxy object that constructs each of these lazily.

Reviewed By: lexs

Differential Revision: D3936979

fbshipit-source-id: 71bde822f01eb17a29f56c5e60e95e98e207d74d

ReactCommon/cxxreact/JSCNativeModules.h

@@ -0,0 +1,35 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+#pragma once
+
+#include <folly/Optional.h>
+
+#include <memory>
+#include <string>
+
+#include "Value.h"
+#include "ModuleRegistry.h"
+
+namespace facebook {
+namespace react {
+
+/**
+ * Holds and creates JS representations of the modules in ModuleRegistry
+ */
+class JSCNativeModules {
+
+public:
+  explicit JSCNativeModules(std::shared_ptr<ModuleRegistry> moduleRegistry);
+  JSValueRef getModule(JSContextRef context, JSStringRef name);
+  void reset();
+
+private:
+  folly::Optional<Object> m_genNativeModuleJS;
+  std::shared_ptr<ModuleRegistry> m_moduleRegistry;
+  std::unordered_map<std::string, Object> m_objects;
+
+  folly::Optional<Object> createModule(const std::string& name, JSContextRef context);
+};
+
+}
+}