在C＃中返回模糊对象

Question

i am currently making a game in my first year of college. I have four enemy objects (Orc, Elf, Goblin, and reptilian) i want to create objects of each enemy depending on the level and room the player is currently in and return object array of that particular enemy. I get the error "the name "enemies" does not exist in the current context". Thank you in advance.

public Object[] level(int lev, int room){
                int enemiesToCreate = 2;
                enemiesToCreate += lev += room;
                if (lev == 1)
                {
                    Goblen[] enemies = new Goblen[enemiesToCreate];
                }
                else if (lev == 2)
                {
                    Orc[] enemies = new Orc[enemiesToCreate];
                }
                else if (lev == 3)
                {
                    Elf[] enemies = new Elf[enemiesToCreate];
                }
                else if (lev == 4)
                {
                    Reptilian[] enemies = new Reptilian[enemiesToCreate];
                }

                // error here
                return enemies;

            }

Answer 1

You must define enemies outside of the if blocks. When you enclose something with {} brackets, it basically creates an additional scope level, typically called a block, that outer levels will not see. So for instance, the following will not work:

if (lev == 1)
{
  Goblen[] enemies = new Goblen[enemiesToCreate];
}

return enemies;

However, if we declare enemies outside of the if block, the return statement will be able to "see" the declaration. For example:

object[] enemies;

if (lev == 1)
{
   enemies = new Goblen[enemiesToCreate];
}

return enemies;

Note that since you are using differing return types, you must use a common base type for the return variable. object always works, though something more specific would be preferable.

Additionally, in this particular situation, you would be better off just skipping the return variable completely and just directly returning from within the if statement, like so:

public Object[] level(int lev, int room){
  int enemiesToCreate = 2;

  enemiesToCreate += lev += room;

  if (lev == 1)
  {
    return new Goblen[enemiesToCreate];
  }
  else if (lev == 2)
  {
    return new Orc[enemiesToCreate];
  }
  ...
  throw new Exception("Unknown enemy type");
}

Answer 2

Make classes Goblen, Orc, Elf, Reptilian inherited from an abstract class or an interface. Declare enemies of that type outside if statements. Probably you will find rewarding the implementation of abstract factory design pattern for your case.