From 1876f64c4ec1bcba8de57b8b5f63e250187b4ad1 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Mon, 23 May 2011 21:20:23 +0300
Subject: [PATCH] Streamline application class registration

---
 source/core/application.cpp | 19 +++++++----------
 source/core/application.h   | 42 ++++++++++++++++++++++++-------------
 2 files changed, 36 insertions(+), 25 deletions(-)

diff --git a/source/core/application.cpp b/source/core/application.cpp
index 17611c1..a588e9d 100644
--- a/source/core/application.cpp
+++ b/source/core/application.cpp
@@ -40,9 +40,9 @@ int Application::run(int argc, char **argv, void *data)
 	}
 	called=true;
 
-	if(!reg_app_)
+	if(!starter_)
 	{
-		cerr<<"Trying to run with no application class registered!\n";
+		cerr<<"Trying to run with no RegisteredApplication class!\n";
 		return 126;
 	}
 
@@ -52,11 +52,11 @@ int Application::run(int argc, char **argv, void *data)
 	{
 		try
 		{
-			app_=reg_app_->create_app(argc, argv);
+			app_=starter_->create_app(argc, argv);
 		}
 		catch(const UsageError &e)
 		{
-			reg_app_->usage(e.what(), argv[0], e.get_brief());
+			starter_->usage(e.what(), argv[0], e.get_brief());
 			return 1;
 		}
 
@@ -144,15 +144,12 @@ void Application::sighandler_(int s)
 }
 
 
-Application::RegBase::RegBase()
+Application::Starter::Starter()
 {
-	if(reg_app_)
-	{
-		cerr<<"Warning: registering the application twice\n";
-		delete reg_app_;
-	}
+	if(starter_)
+		throw InvalidState("Can't create more than one Starter instance");
 
-	reg_app_=this;
+	starter_=this;
 }
 
 Application *Application::app_=0;
diff --git a/source/core/application.h b/source/core/application.h
index 38df732..305fbfe 100644
--- a/source/core/application.h
+++ b/source/core/application.h
@@ -17,29 +17,22 @@ member of type RegApp<MainClass>.
 class Application
 {
 protected:
-	class RegBase
+	class Starter
 	{
-	public:
-		virtual Application *create_app(int, char **)=0;
-		virtual void usage(const char *, const char *, bool)=0;
-		virtual ~RegBase() { }
 	protected:
-		RegBase();
-	};
-
-	template<typename T>
-	class RegApp: public RegBase
-	{
+		Starter();
 	public:
-		Application *create_app(int argc, char **argv) { return new T(argc, argv); }
-		void usage(const char *r, const char *a, bool b) { T::usage(r, a, b); }
+		virtual ~Starter() { }
+
+		virtual Application *create_app(int, char **) = 0;
+		virtual void usage(const char *, const char *, bool) = 0;
 	};
 
 	bool done;
 	int exit_code;
 
 private:
-	static RegBase *reg_app_;
+	static Starter *starter_;
 	static Application *app_;
 	static void *data_;
 
@@ -60,11 +53,32 @@ protected:
 	virtual void sighandler(int) { }
 private:
 	static void sighandler_(int);
+};
 
 	Application(const Application &);
 	Application &operator=(const Application &);
+
+template<typename T>
+class RegisteredApplication: public Application
+{
+private:
+	class Starter: public Application::Starter
+	{
+	public:
+		Application *create_app(int argc, char **argv) { return new T(argc, argv); }
+		void usage(const char *r, const char *a, bool b) { T::usage(r, a, b); }
+	};
+
+	static Starter starter_;
+
+protected:
+	// Force the starter into existence
+	RegisteredApplication() { (void)starter_; }
 };
 
+template<typename T>
+typename RegisteredApplication<T>::Starter RegisteredApplication<T>::starter_;
+
 } // namespace Msp
 
 #endif
-- 
2.43.0