Question

In an actionscript function (method) I have access to arguments.caller which returns a Function object but I can’t find out the name of the function represented by this Function object. Its toString() simply returns [Function] and I can’t find any other useful accessors that give me that… Help :-/

Answer 1

I found an answer and I’ll paste it below.

@fenomas: yes, you are right of course, functions are just objects and what I’m looking for is a the name of the reference to them (if exists, i.e. the function is not anonymous). You also right that in general this doesn’t look like the best way to do programming 😉 But my scenario is special: I want to implement a Checks class (similar to C CHECK) with methods such as Check.checkTrue and Checks.checkRef in which when the check fails I get a nice trace. The traces will appear only in debug version, not in release.

I’m using MTASC and the code below only works with MTASC. It should also be used only for debugging purposes and not release. The technique is to iterate on _global and find a function that’s equal to my calling function. It’s a hack that does not always work (anonymous) but it serves me pretty well in most cases.

39:   /** 40:    * Checks that cond is true. Use this method to validate that condition 41:    * cond holds. 42:    * If cond is false, traces a severe message and returns false to indicate 43:    * check failure. 44:    * 45:    * @param cond the contition expected to be true 46:    * @param msg the message to emit in case the condition is false. 47:    * 48:    * @return false is cond is false 49:    */ 50:   public static function checkTrue(cond:Boolean, msg:String):Boolean { 51:     if (!cond) { 52:       trace('severe', 'CHECK FAILED at ' + 53:           **getFunctionName(arguments.caller)** + ':\n' + msg); 54:     } 55:     return cond; 56:   }   94:   /** 95:    * Gets the name of the function func. 96:    * Warning: Use this only in debug version, not in release 98:    * 99:    * @return The full package path to the function. null if the function 100:    *      isn't found. 101:    */ 102:   private static function getFunctionName(func:Function):String { 103:     var name:String = getFunctionNameRecursive(func, _global); 108:     return name; 109:   } 110:  111:   /** 112:    * Gets the name of the function func by recursively iterating over root. 113:    * Warning: Use this only in debug version, not in release 114:    */ 115:   private static function getFunctionNameRecursive(func:Function, 116:       root:Object):String { 117:     if (!root) { 118:       return null; 119:     } 120:  121:     // Iterate over classes in this package 122:     // A class is a function with a prototype object 123:     for (var i:String in root) { 124:       if (root[i] instanceof Function && root[i].prototype != null) { 125:         // Found a class. 126:         // Iterate over class static members to see if there's a match 127:         for (var f:String in root[i]) { 128:           if(root[i][f] == func) { 129:             return i + '.' + f; 130:           } 131:         } 132:         // Loop over the class's prototype to look for instance methods 133:         var instance:Object = root[i].prototype; 134:         // Reveal prototype's methods. 135:         // Warning: Not to be used in production code!!! 136:         // The following line make all the instance attributes visible to the 137:         // for-in construct. The 'n' value is 8 which means 'unhide' 138:         // See http://osflash.org/flashcoders/undocumented/assetpropflags 139:         // This operation is later undone by setting the 'n' to 1 which means 140:         // 'hide' 141:         _global.ASSetPropFlags(instance, null, 8, 1); 142:         for (var f:String in instance) { 143:           if(instance[f] == func) { 144:             return i + '.' + f; 145:           } 146:         } 147:         // And hide instance methods again 148:         // This line undoes the previous ASSetPropFlags 149:         _global.ASSetPropFlags(instance, null, 1, false); 150:       } 151:     } 152:  153:     // Iterate over sub packages. Sub packages have type 'object' 154:     for (var i:String in root) { 155:       if (typeof(root[i]) == 'object') { 156:         var name:String = getFunctionNameRecursive(func, root[i]); 157:         if (name) { 158:           return i + '.' + name; 159:         } 160:       } 161:     } 162:     return null; 163:   }