add two enemy in one array AS3 - actionscript-3

Question

i want add two enemy an one array for looping, this my code
global_time++;
// generate enemies
if (global_time % 40 == 0) {
enemy = new Enemy();
enemy.x = 40 + Math.random() * 400;
enemy.y = 0;
addChild(enemy);
army.push(enemy);
System.gc();
enemy2 = new Enemy2();
enemy2.x = 40 + Math.random() * 400;
enemy2.y = 0;
addChild(enemy2);
army.push(enemy2);
}
for (var k:int = army.length - 1; k >= 0; k--) {
enemy = army[k];
enemy2 = army[k]
// update all enemies
enemy.update();
enemy2.update2();
// if its out of bound, remove from stage
if (enemy.y < 0) {
army.splice(k, 1);
enemy.parent.removeChild(enemy);
continue;
System.gc();
}
//* enemy2
if (enemy2.y < 0) {
army.splice(k, 1);
enemy2.parent.removeChild(enemy2);
continue;
System.gc();
}
}
when i run this program error "cannot convert Enemy2#501f5e1 to Enemy". please help

Answer 1

The problem is that you have an army with enemies of two different types, Enemy and Enemy2.
In the beginning of the for loop you are picking out the k:th enemy from the army array. This could be either and Enemy or an Enemy2 object, but it cannot be both (unless there is some inheritage which we cannot see).
So what happens in your loop is that you pick out the last enemy, which is of type Enemy2, from the army array, and then you assign that enemy to your variable enemy, which is of type Enemy. This is where the conversion fails.
Probably you should have one Enemy class, and use this for both enemies, but if you want to use two different classes, you would have to do a type checking before operating on your enemy:
for (var k:int = army.length - 1; k >= 0; k--) {
if (army[k] is Enemy) {
enemy = army[k];
enemy.update();
if (enemy.y < 0) {
army.splice(k, 1);
enemy.parent.removeChild(enemy);
continue;
System.gc();
}
} else if (army[k] is Enemy2) {
enemy2 = army[k]
enemy2.update2();
if (enemy2.y < 0) {
army.splice(k, 1);
enemy.parent.removeChild(enemy);
continue;
System.gc();
}
}
}
The best, however, would be to make them inherit from the same base class, i.e.
class Enemy {
public var x;
public var y;
public function update() {...}
}
class Enemy1 extends Enemy {
override public function update() { // Enemy1 special updates }
}
class Enemy2 extends Enemy {
override public function update() { // Enemy2 special updates }
}