Multiple instances of an object/class

Question

I'm making a simple game in VBA excel that's like Rogue or Nethack. It takes place in a gui window. I've got an array to hold the playing field etc. and a class for the player, which has their coordinates stored and some subs to move around etc.

I then created an NPC class that moves around at random. I declared it the usual way, Dim NPC as NPCclass (inside the declarations) and then Set NPC = New NPCclass (inside a sub, which seems to be necessary but none of the tutorials mention that?) So far so good, the NPC is represented by an ASCII character and does what I want it to.

However, now I want to create more NPCs after intervals of a few turns. But I can't figure out how to do it. It seems like for every additional instance of my NPC, I have to do another Dim NPCxyz as NPCclass.

So I tried to generate a string, say "npc_name" that holds the name of the next NPC to be generated, as in NPC1 or NPC2 and so on. Unsurprisingly, if I then try Dim npc_name As NPCclass VBA doesn't understand that I want to create another instance of NPCclass with the string inside npc_name as its name. Instead it thinks I want to declare npc_name again, like when I said Dim npc_name As String earlier.

How can I create more NPCs that use the same class but move independently around the array/playfield? I feel like I'm misunderstanding something obvious because none of the tutorials I looked at went into this.

You are on the right track. The trick here is that as soon as you start thinking "Dynamically named variables" instead think "Arrays" or "Collections". You can have an array of your NPC objects or a collection of your NPC objects. See here for a similar question Personally I would prefer a collection here since it's a little more versatile than an array, although an array would suffice. — JNevill
– JNevill, Commented Apr 6, 2018 at 20:49

Ricardo González · Accepted Answer · 2018-04-06 20:49:13Z

2

Just create an array of objects...

Dim NPC(1 to 20) as NPCclass

For i = 1 to 20
    Set NPC(i) = New NPCclass

    '... your object init ...
    NPC(i).SetSometing = 0
    NPC(i).DoSomething()
Next i

And if later on you want to increase the list you just need to do something like

ReDim Preserve NPC(50)

answered Apr 6, 2018 at 20:49

Ricardo González

1,44311 silver badges21 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Marcelo Gazzola · Accepted Answer · 2019-06-18 09:45:33Z

2

You also can use collections:

Dim NPC as New NPCclass
Dim colNPC as New Collection

for i = 1 to 20
    colNPC.add New NPC
next

edited Jun 18, 2019 at 9:45

answered Jun 17, 2019 at 14:50

Marcelo Gazzola

1,12318 silver badges31 bronze badges

1 Comment

pstraton Over a year ago

Elegant! Much appreciated!

Collectives™ on Stack Overflow

Multiple instances of an object/class

2 Answers 2

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related