AS3 - Abstract Classes

问题:

How can I make an abstract class in AS3 nicely?

I've tried this:

public class AnAbstractClass {     public function toBeImplemented():void     {         throw new NotImplementedError(); // I've created this error     } }  public class AnConcreteClass extends AnAbstractClass {     override public function toBeImplemented():void     {         // implementation...     } } 

But.. I don't like this way. And doesn't have compile time errors.

回答1:

abstract classes are not supported by actionscript 3. see http://joshblog.net/2007/08/19/enforcing-abstract-classes-at-runtime-in-actionscript-3/

the above reference also provides a kind of hackish workaround to create abstract classes in as3.

Edit
also see http://www.kirupa.com/forum/showpost.php?s=a765fcf791afe46c5cf4c26509925cf7&p=1892533&postcount=70

Edit 2 (In response to comment)

Unfortunately, you're stuck with the runtime error. One alternative would be to have a protected constructor.... except as3 doesn't allow that either. See http://www.berniecode.com/blog/2007/11/28/proper-private-constructors-for-actionscript-30/ and http://gorillajawn.com/wordpress/2007/05/21/actionscript-3-%E2%80%93-no-private-constructor/.

You may Also find these useful: http://www.as3dp.com/category/abstract-classes/ and, in particular, http://www.as3dp.com/2009/04/07/design-pattern-principles-for-actionscript-30-the-dependency-inversion-principle/

回答2:

package  {     import flash.errors.IllegalOperationError;     import flash.utils.getDefinitionByName;     import flash.utils.getQualifiedClassName;     import flash.utils.getQualifiedSuperclassName;      public class AbstractClass      {         public function AbstractClass()         {             inspectAbstract();         }          private function inspectAbstract():void          {             var className : String = getQualifiedClassName(this);             if (getDefinitionByName(className) == AbstractClass )              {                 throw new ArgumentError(                 getQualifiedClassName(this) + "Class can not be instantiated.");             }         }          public function foo():void         {             throw new IllegalOperationError("Must override Concreate Class");          }     } } 

---

package {     public class ConcreteClass extends AbstractClass     {         public function ConcreteClass()         {             super();         }          override public function foo() : void          {             trace("Implemented");         }    } } 

回答3:

In AS3 would just use interfaces to make sure all functions are implemented at compile time. I know it different but does the trick for an example such as the one above.

回答4:

As long as they don't permit non-public constructors in actionscript, you'd have to rely on run time errors for abstract classes and singletons.

文章来源: AS3 - Abstract Classes