Implement Value::demand()

Author: res2k

include/json/value.h

@@ -524,7 +524,7 @@ Json::Value obj_value(Json::objectValue); // {}
   /// Most general and efficient version of object-mutators.
   /// \note As stated elsewhere, behavior is undefined if (end-begin) >= 2^30
   /// \return non-zero, but JSON_ASSERT if this is neither object nor nullValue.
-  Value const* demand(char const* begin, char const* end);
+  Value* demand(char const* begin, char const* end);
   /// \brief Remove and return the named member.
   ///
   /// Do nothing if it did not exist.

src/lib_json/json_value.cpp

@@ -1126,6 +1126,12 @@ Value const* Value::find(char const* begin, char const* end) const {
     return nullptr;
   return &(*it).second;
 }
+Value* Value::demand(char const* begin, char const* end) {
+  JSON_ASSERT_MESSAGE(type() == nullValue || type() == objectValue,
+                      "in Json::Value::demand(begin, end): requires "
+                      "objectValue or nullValue");
+  return &resolveReference(begin, end);
+}
 const Value& Value::operator[](const char* key) const {
   Value const* found = find(key, key + strlen(key));
   if (!found)

src/test_lib_json/main.cpp

@@ -214,6 +214,15 @@ JSONTEST_FIXTURE(ValueTest, objects) {
   const Json::Value* foundUnknownId = object1_.find(unknownIdKey, unknownIdKey + strlen(unknownIdKey));
   JSONTEST_ASSERT_EQUAL(nullptr, foundUnknownId);
 
+  const char yetAnotherIdKey[] = "yet another id";
+  const Json::Value* foundYetAnotherId = object1_.find(yetAnotherIdKey, yetAnotherIdKey + strlen(yetAnotherIdKey));
+  JSONTEST_ASSERT_EQUAL(nullptr, foundYetAnotherId);
+  Json::Value* demandedYetAnotherId = object1_.demand(yetAnotherIdKey, yetAnotherIdKey + strlen(yetAnotherIdKey));
+  JSONTEST_ASSERT(demandedYetAnotherId != nullptr);
+  *demandedYetAnotherId = "baz";
+
+  JSONTEST_ASSERT_EQUAL(Json::Value("baz"), object1_["yet another id"]);
+
   // Access through non-const reference
   JSONTEST_ASSERT_EQUAL(Json::Value(1234), object1_["id"]);
   JSONTEST_ASSERT_EQUAL(Json::Value(), object1_["unknown id"]);