base: Add AsList() function to Value API.

This function should simplify some constructions.

Instead of:

if (!value->IsType(Value::TYPE_LIST))
  return false;
ListValue* list_value = static_cast<ListValue*>(value);

You can do:

ListValue* list_value = value->AsList();
if (!list_value)
  return false;

BUG=None
TEST=base_unittests --gtest_filter=Values*

R=evan@chromium.org,tony@chromium.org

Review URL: http://codereview.chromium.org/7714004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@98223 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 11 insertions, 3 deletions

diff --git a/base/values.cc b/base/values.cc
index 17aba16..1798695 100644
--- a/base/values.cc
+++ b/base/values.cc
@@ -97,6 +97,10 @@ StringValue* Value::CreateStringValue(const string16& in_value) {
   return new StringValue(in_value);
 }
 
+ListValue* Value::AsList() {
+  return NULL;
+}
+
 bool Value::GetAsBoolean(bool* out_value) const {
   return false;
 }
@@ -511,7 +515,7 @@ bool DictionaryValue::GetList(const std::string& path,
                               ListValue** out_value) const {
   Value* value;
   bool result = Get(path, &value);
-  if (!result || !value->IsType(TYPE_LIST))
+  if (!result || !value->AsList())
     return false;
 
   if (out_value)
@@ -589,7 +593,7 @@ bool DictionaryValue::GetListWithoutPathExpansion(const std::string& key,
                                                   ListValue** out_value) const {
   Value* value;
   bool result = GetWithoutPathExpansion(key, &value);
-  if (!result || !value->IsType(TYPE_LIST))
+  if (!result || !value->AsList())
     return false;
 
   if (out_value)
@@ -802,7 +806,7 @@ bool ListValue::GetDictionary(size_t index, DictionaryValue** out_value) const {
 bool ListValue::GetList(size_t index, ListValue** out_value) const {
   Value* value;
   bool result = Get(index, &value);
-  if (!result || !value->IsType(TYPE_LIST))
+  if (!result || !value->AsList())
     return false;
 
   if (out_value)
@@ -865,6 +869,10 @@ bool ListValue::Insert(size_t index, Value* in_value) {
   return true;
 }
 
+ListValue* ListValue::AsList() {
+  return this;
+}
+
 bool ListValue::GetAsList(ListValue** out_value) {
   if (out_value)
     *out_value = this;