#include <type_traits>
#include <utility>
+#include <boost/optional.hpp>
+
#include <QDebug>
+#include <QVariant>
#include <QVariantList>
// ---- Function traits --------------------------------------------------------------------------------------------------------------------
namespace detail {
+// Helper for invoking the callable, wrapping its return value in a QVariant (default-constructed if callable returns void).
+// The correct overload is selected via SFINAE.
+template<typename Callable, typename ...Args>
+auto invokeWithArgs(const Callable& c, Args&&... args)
+ -> std::enable_if_t<std::is_void<typename FunctionTraits<Callable>::ReturnType>::value, QVariant>
+{
+ c(std::forward<Args>(args)...);
+ return QVariant{};
+}
+
+template<typename Callable, typename ...Args>
+auto invokeWithArgs(const Callable& c, Args&&... args)
+ -> std::enable_if_t<!std::is_void<typename FunctionTraits<Callable>::ReturnType>::value, QVariant>
+{
+ return QVariant::fromValue(c(std::forward<Args>(args)...));
+}
+
// Helper for unpacking the argument list via an index sequence
template<typename Callable, std::size_t ...Is, typename ArgsTuple = typename FunctionTraits<Callable>::ArgsTuple>
-bool invokeWithArgsList(const Callable& c, const QVariantList& args, std::index_sequence<Is...>)
+boost::optional<QVariant> invokeWithArgsList(const Callable& c, const QVariantList& args, std::index_sequence<Is...>)
{
// Sanity check that all types can be converted
std::array<bool, std::tuple_size<ArgsTuple>::value> convertible{{args[Is].canConvert<std::decay_t<std::tuple_element_t<Is, ArgsTuple>>>()...}};
for (size_t i = 0; i < convertible.size(); ++i) {
if (!convertible[i]) {
qWarning() << "Cannot convert parameter" << i << "from type" << args[static_cast<int>(i)].typeName() << "to expected argument type";
- return false;
+ return boost::none;
}
}
- // Invoke callable
- c(args[Is].value<std::decay_t<std::tuple_element_t<Is, ArgsTuple>>>()...);
- return true;
+ // Invoke callable with unmarshalled arguments
+ return invokeWithArgs(c, args[Is].value<std::decay_t<std::tuple_element_t<Is, ArgsTuple>>>()...);
}
} // detail
* Invokes the given callable with the arguments contained in the given variant list.
*
* The types contained in the given QVariantList are converted to the types expected by the callable.
- * If the conversion fails, or if the argument count does not match, this function returns false and
- * the callable is not invoked.
+ * If the invocation is successful, the returned optional contains a QVariant with the return value,
+ * or an invalid QVariant if the callable returns void.
+ * If the conversion fails, or if the argument count does not match, this function returns boost::none
+ * and the callable is not invoked.
*
* @param c Callable
* @param args Arguments to be given to the callable
- * @returns true if the callable could be invoked with the given list of arguments
+ * @returns An optional containing a QVariant with the return value if the callable could be invoked with
+ * the given list of arguments; otherwise boost::none
*/
template<typename Callable>
-bool invokeWithArgsList(const Callable& c, const QVariantList& args)
+boost::optional<QVariant> invokeWithArgsList(const Callable& c, const QVariantList& args)
{
using ArgsTuple = typename FunctionTraits<Callable>::ArgsTuple;
constexpr auto tupleSize = std::tuple_size<ArgsTuple>::value;
if (tupleSize != args.size()) {
qWarning().nospace() << "Argument count mismatch! Expected: " << tupleSize << ", actual: " << args.size();
- return false;
+ return boost::none;
}
return detail::invokeWithArgsList(c, args, std::make_index_sequence<tupleSize>{});
}
// Good case
{
QVariantList argsList{42, "Hello World"};
- ASSERT_TRUE(invokeWithArgsList(callable, argsList));
+ auto ret = invokeWithArgsList(callable, argsList);
+ ASSERT_TRUE(ret);
+ EXPECT_FALSE(ret->isValid()); // Callable returns void, so the returned QVariant should be invalid
EXPECT_EQ(42, intVal);
EXPECT_EQ("Hello World", stringVal);
}
EXPECT_EQ("Hello World", stringVal);
}
}
+
+TEST(FuncHelpersTest, invokeWithArgsListAndReturnValue)
+{
+ {
+ int intVal{};
+ QString stringVal{};
+
+ auto callable = [&intVal, &stringVal](int i, const QString& s)
+ {
+ intVal = i;
+ stringVal = s;
+ return -i;
+ };
+
+ // Good case
+ {
+ QVariantList argsList{42, "Hello World"};
+ auto ret = invokeWithArgsList(callable, argsList);
+ ASSERT_TRUE(ret);
+ ASSERT_TRUE(ret->isValid());
+ EXPECT_EQ(-42, *ret);
+ EXPECT_EQ(42, intVal);
+ EXPECT_EQ("Hello World", stringVal);
+ }
+
+ // Failed invocation
+ {
+ QVariantList argsList{23};
+ ASSERT_FALSE(invokeWithArgsList(callable, argsList));
+ }
+ }
+}