Question on list collection type

Unity Engine
,
1

Hello,

I have a question on the list collection type that I have no knowledge on, as I am new at coding in C#. Currently, I have stored a bunch of game objects in a list that appear in the game I am making. What I want to do is grab a random game object at the start of the game that is in the list, and then have that selected game object perform an animation every couple of minutes. What I want to know is how to perform this action through the code. Thank you for your time, as I appreciate it.

using System.Collections;
using System.Collections.Generic;
using System.Threading;
using Unity.VisualScripting;
using UnityEngine;

public class ObjectSelect : MonoBehaviour
{
List houseItems = new List ()
{
// Floor 1
“Couch_1”, " Couch_2", " Couch_3", " Bookshelf_1_1", " Bookshelf_1_2",
" Bookshelf_1_3", " TeleV_1",
" D_Table_Sm", " D_Table", " D_Cabinet_1", " D_Cabinet_2",
" Sink_K", " Fridge", " Oven_Top",
" RedCar_Top"
// Floor 2

// Floor 3
};

List GetRandomElements(List inputList, int count)
{
List outputList = new List();
for (int i = 0; i < count; i++)
{
int index = Random.Range(0, inputList.Count);
outputList.Add(inputList[index]);
}
return outputList;
}

void Start()
{
var randomList = GetRandomElements(houseItems, 1);

Debug.Log(“All elements => " + string.Join(”,“, houseItems));
Debug.Log(“Random elements => " + string.Join(”,”, randomList));
Debug.Log(“*****************************”);

Debug.LogFormat(“House Items: {0}”, houseItems.Count);
}

/*
Need to learn code which takes selected game object,

then activates animation for selected game object.
*/
}
[/code]

2

Definitely start with basic tutorials for this stuff, nobody is going to type it all here in this little box!!

Break the problem down into little tiny bite-sized parts and work on them one at a time, like this guy:

Imphenzia: How Did I Learn To Make Games:

Tutorials and example code are great, but keep this in mind to maximize your success and minimize your frustration:

How to do tutorials properly, two (2) simple steps to success:

Step 1. Follow the tutorial and do every single step of the tutorial 100% precisely the way it is shown. Even the slightest deviation (even a single character!) generally ends in disaster. That’s how software engineering works. Every step must be taken, every single letter must be spelled, capitalized, punctuated and spaced (or not spaced) properly, literally NOTHING can be omitted or skipped.
Fortunately this is the easiest part to get right: Be a robot. Don’t make any mistakes.
BE PERFECT IN EVERYTHING YOU DO HERE!!

If you get any errors, learn how to read the error code and fix your error. Google is your friend here. Do NOT continue until you fix your error. Your error will probably be somewhere near the parenthesis numbers (line and character position) in the file. It is almost CERTAINLY your typo causing the error, so look again and fix it.

Step 2. Go back and work through every part of the tutorial again, and this time explain it to your doggie. See how I am doing that in my avatar picture? If you have no dog, explain it to your house plant. If you are unable to explain any part of it, STOP. DO NOT PROCEED. Now go learn how that part works. Read the documentation on the functions involved. Go back to the tutorial and try to figure out WHY they did that. This is the part that takes a LOT of time when you are new. It might take days or weeks to work through a single 5-minute tutorial. Stick with it. You will learn.

Step 2 is the part everybody seems to miss. Without Step 2 you are simply a code-typing monkey and outside of the specific tutorial you did, you will be completely lost. If you want to learn, you MUST do Step 2.

Of course, all this presupposes no errors in the tutorial. For certain tutorial makers (like Unity, Brackeys, Imphenzia, Sebastian Lague) this is usually the case. For some other less-well-known content creators, this is less true. Read the comments on the video: did anyone have issues like you did? If there’s an error, you will NEVER be the first guy to find it.

Beyond that, Step 3, 4, 5 and 6 become easy because you already understand!

Finally, when you have errors, don’t post here… just go fix your errors! Here’s how:

Remember: NOBODY here memorizes error codes. That’s not a thing. The error code is absolutely the least useful part of the error. It serves no purpose at all. Forget the error code. Put it out of your mind.

The complete error message contains everything you need to know to fix the error yourself.

The important parts of the error message are:

  • the description of the error itself (google this; you are NEVER the first one!)
  • the file it occurred in (critical!)
  • the line number and character position (the two numbers in parentheses)
  • also possibly useful is the stack trace (all the lines of text in the lower console window)

Always start with the FIRST error in the console window, as sometimes that error causes or compounds some or all of the subsequent errors. Often the error will be immediately prior to the indicated line, so make sure to check there as well.

Look in the documentation. Every API you attempt to use is probably documented somewhere. Are you using it correctly? Are you spelling it correctly? Are you structuring the syntax correctly? Look for examples!

All of that information is in the actual error message and you must pay attention to it. Learn how to identify it instantly so you don’t have to stop your progress and fiddle around with the forum.

If you get stuck, here is how to report your problem productively in the Unity3D forums:

http://plbm.com/?p=220

This is the bare minimum of information to report:

  • what you want
  • what you tried
  • what you expected to happen
  • what actually happened, log output, variable values, and especially any errors you see
  • links to actual Unity3D documentation you used to cross-check your work (CRITICAL!!!)

The purpose of YOU providing links is to make our job easier, while simultaneously showing us that you actually put effort into the process. If you haven’t put effort into finding the documentation, why should we bother putting effort into replying?

If you post a code snippet, ALWAYS USE CODE TAGS:

How to use code tags: Using code tags properly

  • Do not TALK about code without posting it.
  • Do NOT post unformatted code.
  • Do NOT retype code. Use copy/paste properly using code tags.
  • Do NOT post screenshots of code.
  • Do NOT post photographs of code.
  • Do NOT attach entire scripts to your post.
  • ONLY post the relevant code, and then refer to it in your discussion.
3

Grabbing a random item from a List/Array/Collection is an extremely known and used system in game development. A simple Google search/GPT prompt will give you the reply.

I’d say the first and most important skill you want to have and master to become a (game) developer is Googling/searching/finding solutions to your current problem (which has a 99% chance of already being solved and a solution available on internet).

Anyway, the answer is simple:

// this returns an integer between [0] and the [total number of items in your list minus 1]
int randomIndex = UnityEngine.Random(0, yourList.Count);
// let's get the item at that random index...
string randomItem = yourList[randomIndex];

And if you need to do this often, you can create your own helper class to do it:

public static class RandomHelper
{
    public static T GetRandomItem<T>(IReadOnlyList<T> items)
    {
        return items[UnityEngine.Random(0, items.Count)];
    }
}

And now you have a generic RandomHelper.GetRandomItem method you can call on any array/list of any type to get a random item…

string randomString = RandomHelper.GetRandomItem(listOfStrings);
Transform randomTransform = RandomHelper.GetRandomItem(arrayOfTransforms);
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