ActionScript 3
Korzystanie z klasy proxy

Wprowadzenie

Realizacja

Inną rzeczą dotyczącą klasy Proxy i tego, dlaczego nie jest ona tak popularna, jest to, że trudno jest pojąć problem, który dokładnie potrzebuje klasy dynamicznej z kontrolowanym dostępem do jej właściwości dynamicznych i metod jako najbardziej odpowiedniego rozwiązania. Za każdym razem, gdy próbowałem używać proxy, korzystałem z czegoś innego, prostszego i bardziej kontrolowanego.

Nie zniechęcajmy się jednak. Podoba mi się pomysł adresowania ostatnich elementów tablicy za pomocą indeksów [-1], [-2] itp. W Pythonie . To może nie być duży wyczyn, ale fajnie jest używać tego zamiast długiego i niezdarnego someArray [someArray.length - 1] . Zobaczmy, co możemy z tym zrobić.

package
{
    import flash.utils.Proxy;
    import flash.utils.flash_proxy;
    
    /**
     * Pyaray the Tentacled Whisperer of Impossible Secrets.
     */
    
    dynamic public class PyArray extends Proxy
    {
        private var data:Array;
        
        public function PyArray(...args:Array)
        {
            if (args.length == 0)
            {
                data = new Array;
            }
            else if ((args.length == 1) && (args[0] is Array))
            {
                data = args[0];
            }
            else
            {
                data = args;
            }
        }
        
        // This is a getter proxy to all the available Array
        // elements and properties and, sometimes, methods.
        override flash_proxy function getProperty(name:*):*
        {
            var anIndex:int = name;
            
            // Handle the int indices of the Array elements.
            if (anIndex == name)
            {
                // Handle the -1, -2, etc indexing.
                if (anIndex < 0) anIndex += data.length;
                
                if (anIndex >= data.length) return null;
                if (anIndex < 0) return null;
                
                return data[anIndex];
            }
            
            // Handle the existing public Array properties.
            if (data.hasOwnProperty(name)) return data[name];
            
            // Handle the Array methods addressed via ["member"] access.
            try
            {
                if (data[name] is Function) return data[name];
                else throw new Error;
            }
            catch (fail:Error)
            {
                trace("[PyArray] is unable to resolve property \"" + name + "\".");
            }
            
            return null;
        }
        
        // This will set either elements, or settable properties.
        override flash_proxy function setProperty(name:*, value:*):void
        {
            var anIndex:int = name;
            
            // Handle the int indices of the Array elements.
            if (anIndex == name)
            {
                // Handle the -1, -2, etc indexing.
                if (anIndex < 0) anIndex += data.length;
                
                // In case the element index is out of range,
                // the PyArray will extend its data Array.
                // if (anIndex >= data.length) return;
                if (anIndex < 0) return;
                
                data[anIndex] = value;
                
                return;
            }
            
            // Handle the existing (or dynamic) public Array properties.
            try
            {
                data[name] = value;
            }
            catch (fail:Error)
            {
                trace("[PyArray] is unable to set property \"" + name + "\".");
            }
            
            return;
        }
        
        // This allows to delete PyArray elements with "delete" operator.
        override flash_proxy function deleteProperty(name:*):Boolean
        {
            var anIndex:int = name;
            
            // Handle the int indices of the Array elements.
            if (anIndex == name)
            {
                // Handle the -1, -2, etc indexing.
                if (anIndex < 0) anIndex += data.length;
                
                if (anIndex >= data.length) return false;
                if (anIndex < 0) return false;
                
                data.splice(anIndex, 1);
                
                return true;
            }
            
            // Handle the dynamic public Array properties.
            try
            {
                delete data[name];
                return true;
            }
            catch (fail:Error)
            {
                trace("[PyArray] is unable to delete the \"" + name + "\" property.");
            }
            
            return false;
        }
        
        // This proxies any attempt to call a method on PyArray directly to data Array, thus
        // all Array methods (including "toString" method called through trace) are available.
        override flash_proxy function callProperty(name:*, ...rest):*
        {
            try
            {
                return (data[name] as Function).apply(data, rest);
            }
            catch (fail:Error)
            {
                trace("[PyArray] is unable to resolve method \"" + name + "\".");
                return null;
            }
        }
        
        // This allows PyArray to handle for..in and for..each..in loops.
        // The initial call starts with zero, so we need to do this +1 -1 magic
        // in order for enumeration to work correctly. I'm not happy with this either.
        override flash_proxy function nextNameIndex(index:int):int
        {
            if (index >= data.length) return 0;
            else return index + 1;
        }
        
        // This method handles the for..in loop.
        override flash_proxy function nextName(index:int):String
        {
            return (index - 1).toString();
        }
        
        // This method handles the for..each..in loop.
        override flash_proxy function nextValue(index:int):*
        {
            return data[index - 1];
        }
    }
}

Stosowanie

package
{
    import flash.display.Sprite;
    
    /**
     * Daemonette of Slaanesh.
     * 
     * It is minor female demon, vaguely human-like, but with crab-like pincers instead of hands.
     * She wears a rather indecent skimpy leather bikini, moves quickly and casts deadly spells!
     */
    
    public class Slaanesh extends Sprite
    {
        public function Slaanesh() 
        {
            // Lets initialize the PyArray.
            var PA:PyArray = new PyArray(1,2,3,4,5,4,3,2,1,"Foo");
            
            // Basic check: get the last element.
            trace(PA[-1]);
            // output:
            // Foo
            
            // This will map to the 0-based third element.
            trace(PA[2.0]);
            // output:
            // 3
            
            // This should not get us anywhere.
            trace(PA[2.1]);
            // output:
            // [PyArray] is unable to resolve property "2.1".
            // null
            
            // This should return the length of the data Array.
            trace(PA["length"]);
            // output:
            // 10
            
            // This should return the length of the data Array.
            // This will not compile unless PyArray class is marked "dynamic".
            trace(PA.length);
            // output:
            // 10
            
            // This will map to indexOf method of data Array via getProperty method.
            trace(PA["indexOf"]);
            // output:
            // function Function() {}
            
            // This will map to indexOf method of data Array via getProperty method.
            // This will not compile unless PyArray class is marked "dynamic".
            trace(PA.indexOf);
            // output:
            // function Function() {}
            
            // This is a try to access a non-existent property.
            // This will not compile unless PyArray class is marked "dynamic".
            trace(PA.P124);
            // output:
            // [PyArray] is unable to resolve property "P124".
            // null
            
            // This is a try to call a non-existent method via callProperty method.
            // This will not compile unless PyArray class is marked "dynamic".
            trace(PA.P124());
            // output:
            // [PyArray] is unable to resolve method "P124".
            // null
            
            // Basic check: calling a proxied method via callProperty method.
            trace(PA.indexOf(5));
            // output:
            // 4
            
            // An attempt to replace an Array method with a random value.
            // This will not compile unless PyArray class is marked "dynamic".
            PA.indexOf = 123;
            // output:
            // [PyArray] is unable to set property "indexOf".
            
            // An attempt to assign a random value to a random property.
            // It will succees because Array, as a dynamic class, allows so.
            // This will not compile unless PyArray class is marked "dynamic".
            PA.indexOfz = 123;
            trace(PA.indexOfz);
            // output:
            // 123
            
            // An attempt to assign an Array element via negative indexing.
            // This trace works fine because toString method is also proxied.
            PA[-3] = "Hello";
            trace(PA);
            // output:
            // 1,2,3,4,5,4,3,Hello,1,Foo
            
            // An attempt to delete Array elements via normal and negative indexing.
            // This operation is mapped via deleteProperty method.
            delete PA[-4]; // deletes "3" before "Hello"
            delete PA[0];  // deletes "1" at the start.
            trace(PA);
            // output:
            // 2,3,4,5,4,Hello,1,Foo
            
            // An attempt to delete a non-dynamic method reference.
            // There's no error output, AS3 must be handling this internally.
            delete PA.indexOf;
            trace(PA.indexOf);
            // output:
            // function Function() {}
            
            // An attempt to set an element out of index range.
            PA[10] = "123abc";
            trace(PA);
            // output:
            // 2,3,4,5,4,Hello,1,Foo,,,123abc
            
            var aText:String;
            
            // This is a test of for..in loop, Array elements are
            // enumerated via nextName and nextNameIndex methods.
            aText = ""
            
            for (var aKey:String in PA)
                aText += aKey + ":" + PA[aKey] + " ";
            
            trace(aText);
            // output:
            // 0:2 1:3 2:4 3:5 4:4 5:Hello 6:1 7:Foo 8:undefined 9:undefined 10:123abc 
            
            // This is a test of for..each..in loop, Array elements are
            // enumerated via nextValue and nextNameIndex methods.
            aText = "";
            
            for each (var aValue:* in PA)
                aText += aValue + " ";
            
            trace(aText);
            // output:
            // 2 3 4 5 4 Hello 1 Foo undefined undefined 123abc
        }
    }
}