A simple Flash assert class. Where's a preprocessor when you need one...

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@4876 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/as/com/threerings/util/Assert.as

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+//
+// $Id$
+//
+// Narya library - tools for developing networked games
+// Copyright (C) 2002-2007 Three Rings Design, Inc., All Rights Reserved
+// http://www.threerings.net/code/narya/
+//
+// This library is free software; you can redistribute it and/or modify it
+// under the terms of the GNU Lesser General Public License as published
+// by the Free Software Foundation; either version 2.1 of the License, or
+// (at your option) any later version.
+//
+// This library 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
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+
+package com.threerings.util {
+
+import flash.system.Capabilities;
+
+/**
+ * Simple implementation of assertion checks for debug environments.
+ * When running in a debug player, each function will test the assert expression,
+ * and if it fails, log an error message with a stack trace. When running in a
+ * release player, these functions do not run any tests, and exit immediately.
+ *
+ * Note: stack dumping is controlled via the Assert.dumpStack parameter.
+ *
+ * Usage example:
+ * <pre>
+ *   Assert.isNotNull(mystack.top());
+ *   Assert.isTrue(mystack.length == 1, "Unexpected number of items on stack!");
+ * </pre>
+ */
+public class Assert
+{
+    /** Controls whether stack dumps should be included in the error log (default value is true).*/
+    public static var dumpStack :Boolean = true;
+    
+    /** Asserts that the value is equal to null. */
+    public static function isNull (value :*, message :String = null) :void
+    {
+        if (_debug && ! (value == null)) {
+            fail(message);
+        }
+    }
+
+    /** Asserts that the value is not equal to null. */
+    public static function isNotNull (value :*, message :String = null) :void
+    {
+        if (_debug && ! (value != null)) {
+            fail(message);
+        }
+    }
+
+    /** Asserts that the value is false. */
+    public static function isFalse (value :Boolean, message :String = null) :void
+    {
+        if (_debug && value) {
+            fail(message);
+        }
+    }
+    
+    /** Asserts that the value is true. */
+    public static function isTrue (value :Boolean, message :String = null) :void
+    {
+        if (_debug && ! value) {
+            fail(message);
+        }
+    }
+
+    /** Displays an error message, with an optional stack trace. */
+    public static function fail (message :String) :void
+    {
+        _log.warning("Failure" + ((message != null) ? (": " + message) : ""));
+        if (dumpStack) {
+            _log.warning(new Error("dumpStack").getStackTrace());
+        }
+    }        
+
+    protected static var _log :Log = Log.getLog(Assert);
+    protected static var _debug :Boolean = Capabilities.isDebugger;
+}
+}