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engines/ultima/ultima4/core/observer.h

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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef ULTIMA4_CORE_OBSERVER_H
+#define ULTIMA4_CORE_OBSERVER_H
+
+namespace Ultima {
+namespace Ultima4 {
+
+template<class O, class A>
+class Observable;
+class NoArg;
+
+/**
+ * This is the interface a class must implement to watch an
+ * Observable.
+ */
+template<class O, class A = NoArg *>
+class Observer {
+public:
+	virtual void update(O observable, A arg) = 0;
+	virtual ~Observer() {}
+};
+
+/**
+ * A specialized observer for watching observables that don't use the
+ * "arg" parameter to update.
+ */
+template<class O>
+class Observer<O, NoArg *> {
+public:
+	virtual void update(O observable, NoArg *arg) {
+		update(observable);
+	}
+	virtual void update(O observable) = 0;
+	virtual ~Observer() {}
+};
+
+/**
+ * Just an empty marker class to identify observers that take no args
+ * on update.
+ */
+class NoArg {
+};
+
+} // End of namespace Ultima4
+} // End of namespace Ultima
+
+#endif