“可能未定义的方法”的原因

Question

我正在研究一本书（ActionScript 3.0 设计模式，O'Reilly）中的 Space Invaders 示例，并且我已经很好地弄清楚了事情，只是现在我看到了

internal/space-invaders/trunk/ship/ShipFactory.as, Line 11  1180: Call to a possibly undefined method drawShip.
internal/space-invaders/trunk/ship/ShipFactory.as, Line 12  1180: Call to a possibly undefined method setPosition.
internal/space-invaders/trunk/ship/ShipFactory.as, Line 14  1180: Call to a possibly undefined method initShip.

并且我不知道为什么。范围界定？遗传不好？包可见性？我是否误解了AS3的多态性规则？这里（按顺序）是基类、子类和工厂类：

Ship.as 中的基类：

package ship {
    import flash.display.Sprite;

    class Ship extends Sprite {

        function setPosition(x:int, y:int):void {
            this.x = x;
            this.y = y;
        }

        function drawShip( ):void { }

        function initShip( ):void { }

    }

}

HumanShip.as 中的子类：

package ship {
    import weapon.HumanWeapon;
    import flash.events.MouseEvent;

    class HumanShip extends Ship {

        private var weapon:HumanWeapon;

        override function drawShip( ):void {
            graphics.beginFill(0x00ff00);
            graphics.drawRect(-5, -15, 10, 10);
            graphics.drawRect(-12, -5, 24, 10);
            graphics.drawRect(-20, 5, 40, 10);
            graphics.endFill();
        }

        override function initShip( ):void {
            weapon = new HumanWeapon();
            this.stage.addEventListener(MouseEvent.MOUSE_MOVE, this.moveShip);
            this.stage.addEventListener(MouseEvent.MOUSE_DOWN, this.fire);
        }

        protected function moveShip(event:MouseEvent):void {
            trace('MOVE');
            this.x = event.stageX;
            event.updateAfterEvent();
        }

        protected function fire(event:MouseEvent):void {
            trace('FIRE');
            weapon.fire(HumanWeapon.MISSILE, this.stage, this.x, this.y - 25);
            event.updateAfterEvent();
        }

    }

}

Ship.as 中的工厂类>ShipFactory.as：

package ship {
    import flash.display.Stage;

    public class ShipFactory {

        public static const HUMAN:uint = 0;
        public static const ALIEN:uint = 1;

        public function produce(type:uint, target:Stage, x:int, y:int):void {
            var ship:Ship = this.createShip(type);
            ship.drawShip();
            ship.setPosition(x, y);
            target.addChild(ship);
            ship.initShip();
        }

        private function createShip(type:uint):Ship {
            switch (type) {
                case HUMAN: return new HumanShip();
                case ALIEN: return new AlienShip();
                default:
                    throw new Error('Invalid ship type in ShipFactory::createShip()');
                    return null;
            }
        }

    }

}

Answer 1

唯一让我惊讶的是你的“Ship”基类中的方法没有访问修饰符。尝试明确地将它们公开！我不确定 AS3 默认值是什么，如果未指定访问修饰符，它们可能会被视为受保护。