[GitHub] [arrow] pitrou commented on a change in pull request #8309: ARROW-7372: [C++] Allow creating dictionary array from simple JSON

[GitBox <gi...@apache.org>]

pitrou commented on a change in pull request #8309:
URL: https://github.com/apache/arrow/pull/8309#discussion_r498099713



##########
File path: cpp/src/arrow/ipc/json_simple.cc
##########
@@ -50,13 +51,35 @@ namespace json {
 using ::arrow::internal::checked_cast;
 using ::arrow::internal::checked_pointer_cast;
 
-static constexpr auto kParseFlags = rj::kParseFullPrecisionFlag | rj::kParseNanAndInfFlag;
+namespace {
 
-static Status JSONTypeError(const char* expected_type, rj::Type json_type) {
+constexpr auto kParseFlags = rj::kParseFullPrecisionFlag | rj::kParseNanAndInfFlag;
+
+Status JSONTypeError(const char* expected_type, rj::Type json_type) {
   return Status::Invalid("Expected ", expected_type, " or null, got JSON type ",
                          json_type);
 }
 
+template <typename Type>
+struct RegularBuilderTraits {
+  using BuilderType = typename TypeTraits<Type>::BuilderType;
+
+  static const std::shared_ptr<DataType>& value_type(
+      const std::shared_ptr<DataType>& type) {
+    return type;
+  }
+};
+
+template <typename Type>
+struct DictionaryBuilderTraits {
+  using BuilderType = DictionaryBuilder<Type>;
+
+  static const std::shared_ptr<DataType>& value_type(
+      const std::shared_ptr<DataType>& type) {
+    return checked_cast<const DictionaryType&>(*type).value_type();
+  }
+};
+

Review comment:
       Ah, right, thank you.




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