Use visitor instead of pulling values directly

Sensor thresholds pull out an int64_t and immediately
assign it to a double. Use a visitor instead to avoid
the intermediate and add flexibility / saftey to type
readings.

Tested-By: Verifed sensor list still worked.
Change-Id: If49bf54ec1c0636b3549d433b86ecdbd1ea99b0d
Signed-off-by: James Feist <james.feist@linux.intel.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/utils.hpp b/utils.hpp
index 75a3252..535ea66 100644
--- a/utils.hpp
+++ b/utils.hpp
@@ -208,6 +208,27 @@ ObjectTree getAllAncestors(sdbusplus::bus::bus& bus,
                            const std::string& path,
                            InterfaceList&& interfaces);
 
+/** @struct VariantToDoubleVisitor
+ *  @brief Visitor to convert variants to doubles
+ *  @details Performs a static cast on the underlying type
+ */
+struct VariantToDoubleVisitor
+{
+    template <typename T>
+    std::enable_if_t<std::is_arithmetic<T>::value, double>
+    operator()(const T &t) const
+    {
+        return static_cast<double>(t);
+    }
+
+    template <typename T>
+    std::enable_if_t<!std::is_arithmetic<T>::value, double>
+    operator()(const T &t) const
+    {
+        throw std::invalid_argument("Cannot translate type to double");
+    }
+};
+
 namespace method_no_args
 {