Split get_default() into two for deferred default construction and added forwarding...

[folly.git] / folly / MapUtil.h

diff --git a/folly/MapUtil.h b/folly/MapUtil.h
index b1fbfadcaf59ecf3db6d14e80f35e472152fa249..433489273785a6f2677c6f36563ea2a292d8fb58 100644 (file)
--- a/folly/MapUtil.h
+++ b/folly/MapUtil.h
@@ -18,6 +18,7 @@
 
 #include <folly/Conv.h>
 #include <folly/Optional.h>
+#include <folly/functional/Invoke.h>
 #include <tuple>
 
 namespace folly {
@@ -26,13 +27,21 @@ namespace folly {
  * Given a map and a key, return the value corresponding to the key in the map,
  * or a given default value if the key doesn't exist in the map.
  */
-template <class Map, typename Key = typename Map::key_type>
-typename Map::mapped_type get_default(
-    const Map& map,
-    const Key& key,
-    const typename Map::mapped_type& dflt = typename Map::mapped_type()) {
+template <typename Map, typename Key>
+typename Map::mapped_type get_default(const Map& map, const Key& key) {
   auto pos = map.find(key);
-  return (pos != map.end() ? pos->second : dflt);
+  return (pos != map.end()) ? (pos->second) : (typename Map::mapped_type{});
+}
+template <
+    class Map,
+    typename Key = typename Map::key_type,
+    typename Value = typename Map::mapped_type,
+    typename std::enable_if<!is_invocable<Value>::value>::type* = nullptr>
+typename Map::mapped_type
+get_default(const Map& map, const Key& key, Value&& dflt) {
+  using M = typename Map::mapped_type;
+  auto pos = map.find(key);
+  return (pos != map.end()) ? (pos->second) : M(std::forward<Value>(dflt));
 }
 
 /**