Added explicit operator bool()

Author: apples

include/json/value.h

@@ -385,6 +385,9 @@ Json::Value obj_value(Json::objectValue); // {}
   /// Return isNull()
   bool operator!() const;
 
+  /// Return !isNull()
+  explicit operator bool() const;
+
   /// Remove all object members and array elements.
   /// \pre type() is arrayValue, objectValue, or nullValue
   /// \post type() is unchanged

src/lib_json/json_value.cpp

@@ -927,6 +927,8 @@ bool Value::empty() const {
 
 bool Value::operator!() const { return isNull(); }
 
+Value::operator bool() const { return !isNull(); }
+
 void Value::clear() {
   JSON_ASSERT_MESSAGE(type_ == nullValue || type_ == arrayValue ||
                           type_ == objectValue,