[commands] Fix C++ Select() factory (#5024)

Update example to use it.

wpilibNewCommands/src/main/native/include/frc2/command/Commands.h

@@ -6,8 +6,10 @@
 
 #include <functional>
 #include <initializer_list>
+#include <memory>
 #include <span>
 #include <string>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -156,13 +158,15 @@ namespace cmd {
  * @param selector the selector function
  * @param commands map of commands to select from
  */
-template <typename Key>
-[[nodiscard]] CommandPtr Select(
-    std::function<Key()> selector,
-    std::vector<std::pair<Key, CommandPtr>> commands) {
-  return SelectCommand(std::move(selector),
-                       CommandPtr::UnwrapVector(std::move(commands)))
-      .ToPtr();
+template <typename Key, class... Types>
+[[nodiscard]] CommandPtr Select(std::function<Key()> selector,
+                                std::pair<Key, Types>&&... commands) {
+  std::vector<std::pair<Key, std::unique_ptr<Command>>> vec;
+
+  ((void)vec.emplace_back(commands.first, std::move(commands.second).Unwrap()),
+   ...);
+
+  return SelectCommand(std::move(selector), std::move(vec)).ToPtr();
 }
 
 // Command Groups

wpilibcExamples/src/main/cpp/examples/SelectCommand/cpp/RobotContainer.cpp

@@ -17,5 +17,5 @@ void RobotContainer::ConfigureButtonBindings() {
 
 frc2::Command* RobotContainer::GetAutonomousCommand() {
   // Run the select command in autonomous
-  return &m_exampleSelectCommand;
+  return m_exampleSelectCommand.get();
 }

wpilibcExamples/src/main/cpp/examples/SelectCommand/include/RobotContainer.h

@@ -5,8 +5,7 @@
 #pragma once
 
 #include <frc2/command/Command.h>
-#include <frc2/command/PrintCommand.h>
-#include <frc2/command/SelectCommand.h>
+#include <frc2/command/Commands.h>
 
 /**
  * This class is where the bulk of the robot should be declared.  Since
@@ -36,12 +35,12 @@ class RobotContainer {
   // value returned by the selector method at runtime.  Note that selectcommand
   // takes a generic type, so the selector does not have to be an enum; it could
   // be any desired type (string, integer, boolean, double...)
-  frc2::SelectCommand<CommandSelector> m_exampleSelectCommand{
+  frc2::CommandPtr m_exampleSelectCommand = frc2::cmd::Select<CommandSelector>(
       [this] { return Select(); },
       // Maps selector values to commands
-      std::pair{ONE, frc2::PrintCommand{"Command one was selected!"}},
-      std::pair{TWO, frc2::PrintCommand{"Command two was selected!"}},
-      std::pair{THREE, frc2::PrintCommand{"Command three was selected!"}}};
+      std::pair{ONE, frc2::cmd::Print("Command one was selected!")},
+      std::pair{TWO, frc2::cmd::Print("Command two was selected!")},
+      std::pair{THREE, frc2::cmd::Print("Command three was selected!")});
 
   void ConfigureButtonBindings();
 };