#List, Find and Lambda Expressions

1 messages · Page 1 of 1 (latest)

spring trench
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Let's talk here

gloomy lily
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Nice

spring trench
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List.Find() uses something called Lambda expressions

Example:

var found = myList.Find(x => x.name == "Bob");
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For advanced cases, multiple variables (x,y) can be used.
I forget what was a good example for that.

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So regarding Arrays and Lists, some basics, just to make sure you have it all covered:

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Arrays and Lists must be initialized before they can hold items.
An array must be initialized with a fixed number of item slots.
Arrays cannot be resized. They must be reconstructed.

// Initialize empty or with hardcoded values
string[] myStrings = new string[3];
string[] myStrings = new string[] { "Hard", "Coded", "Values" ;}
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__A List __ just needs to be initialized with the correct type.
It's size is dynamic, and you just use .Add() .Remove() methods to manage its items.

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List<string> myList = new List<string>();
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A List can also be initialized with an existing array

string[] myStrings = new string[] { "Hard", "Coded", "Values" ;}
List<string> myList = new List<string>(myStrings);
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Finally, you can make a list into an array by myList.ToArray()

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Do you know how to loop through a list?

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I can also stop overexplaining and get to the point, if you feel that's better.

gloomy lily
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Well I dont quite know how you mean loop through it, maybe you meant in different context but the only way I know how to loop for now is just to create a bunch of new indexes in lists. If ofcourse this is correct way to insert them into the list, not sure:

In this case I have 31 items and I all inserted them in a list through a loop so I can access them later. Sorry I am really new at this this programming this is really hard for me but I want to learn it

unknown.png
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No its okay, I would like to know everything to be honest

spring trench
gloomy lily
spring trench
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The only thing you change in that thing is length
if it's an array: myArray.Length
if it's a List: myList.Count

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as long as it is i < length
you don't need to offset the index
(if Count is 10, the highest index is 9, because index starts at 0)

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Length or Count = Number of items

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_
In the first loop you posted you are using Lista to iterate the loop
But the power of the for-loop is that it comes with a local variable, and it is all defined on a single line.

local variables only exist inside their parent method
and they are faster to access than the other variables, which are called fields

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_
fields are stored in the heap
local variables are stored in the stack (faster memory)

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private int field = 0; // Heap

private void Awake()
{
    int local = 0; // Stack
}
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Fixed*

gloomy lily
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ok so if i understand this correctly local variable in this case would be "i" and its used inside the for loop only? This "i" is what I mean in the picture below:

In this case I dont have to actually assign Lista I can just assign some local variable and use it inside the for loop if I understood everything correctly

unknown.png
spring trench
gaunt comet
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if you nest for loops. you'll need a different iterator identifier

gloomy lily
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Ok I see, thats very good to know

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Didnt know about these stuff

spring trench
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Later on you can explore foreach
As long as you're not doing things that require math working with the value of i

If you need to sort a list, I recommend using the System.Linq namespace to enable Linq extensions.
Then you can do myList.SortBy().ThenBy()

Anyway. That's a lot of information to absorb.
Do you have any other specific questions?

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(Fixed some code examples above.
I was making Lists with no names :P)

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List<string> = new List<string>(myStrings); // Was wrong
List<string> myList = new List<string>(myStrings); // Correct
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Forgot to add this:

// Last index
array[array.Length - 1]
myList[myList.Count - 1]
gloomy lily
spring trench
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I'll keep an eye on this thread for a while.
Come back if you get stuck.
(Mind it's Saturday, so anything can happen)

gaunt comet
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you can sure. but this list is not tied to any game object

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its just a list of strings

spring trench
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Perhaps we should take a look at your current example

gloomy lily
# spring trench You can do it either by [index] or Find Beware you cannot delete multiple items...

Oh I see, thats unfortunate that it shifts I guess I will have to figure it out somehow. Maybe then I will just change its color template to invisible from 255 to 0 maybe thats a better solution.

Thanks man, I really appreciate your time. Thats amazing the stuff you told me, its hard to find all that online, only in bits and pieces that you have to connect together yourself. I really really appreciate your help. Cant thank you enough.

Well what im doing at the moment is basically a health bar and a sprint bar. As you can see each bar contains atleast 32 smaller bars (red and green ones). So now im currently just at the health bar and I want to make a list of all those bars which are all game objects manually copy pasted into scene. Now this is around 32 objects and I have to add them to the list and then delete them when the character gets hit. I think I will just change the colors of the bars to invisible in this case not actually delete them because later I will also implement health packs which I will pick up to regain health.

unknown.png
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One question. How do you know who to explain stuff so that the knowledge you tell is not wasted. I imagine atleast 90% of the game developers quit in the first week or so because its overwhelming and they dont know how to get to the knowledge properly. Most of them are just watching tutorials which they copy from and learn nothing.

spring trench
# gloomy lily One question. How do you know who to explain stuff so that the knowledge you tel...

I think a good recipe is just to do some basic tutorials and then start talking with people in Discord as you fix each thing, one by one.
Having a mentor is valuable. Not everyone has one, so Discord and people with free time (who were also helped once) is the next best thing. And you get the benefit of multiple perspectives.

Learning basic C# first is best. You should join the CSharp discord (can't link it here, because spam bots).

Learning to explain things is difficult.
But I found one clue to easier learn things myself, is to think with the correct words, so that the language starts making sense, and my sentences (code ideas) complete themselves.

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You can practice this easily by spending time to thoroughly explain your issue from top to bottom, in a single condensed post (as I've seen you do).
Many times this has helped me solve the problem and just deleting my post, or not posting at all.

spring trench
spring trench
# gloomy lily Oh I see, thats unfortunate that it shifts I guess I will have to figure it out ...

--> Health Bar
Destroying game objects creates garbage (literally, the garbage collector has to clean it up; bad for performance)
And since you will be needing them again, you can just make them invisible, or use gameObject.SetActive(false)

You can have literal tens or hundreds of thousands of game objects in your scene at the same time.
So don't worry about performance until it becomes an issue.

If they were bullets, you would make an object pooling system.
Which means you keep a List of the items as you spawn more (or a set amount), and disable them until needed again.

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Do you have an idea for how to get the smaller bars in a list?

gloomy lily
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Or do you mean like in a list on script?

spring trench
gloomy lily
spring trench
# gloomy lily Yes

you can put a script on the parent
or identify the parent in another script

and use myParent.GetComponent__s__InChildren<GameObject>();

gloomy lily
spring trench
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There are a couple of things to note

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By default, it does not include inactive game objects
but you can make it ...<GameObject>(true)

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Plus, an annoying thing about GetComponentsInChildren, is that it will also include the parent 🤦

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That is where foreach can be a solution

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(You can just code for ignoring or removing the first/parent)

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// Inspector drag-n-drop
[SerializeField] private Transform parent;

private List<Transform> children;

private void Start()
{
    children = new List<Transform>();

    foreach (Transform child in parent)
    {
        children.Add(child);
    }
}

Type fore and Tab twice for auto-complete

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It is worth to note that if you are working with more components than just Transform or GameObject,
for example Rigidbody, or a Script, then it is best to Get that component instead.
Because any component on the object can reference both .transform and .gameObject

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Thus, if you do GetComponentsInChildren<Rigidbody>();
it will only add the objects that actually have a Rigidbody (often ignoring the parent)

gloomy lily
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So I figured it out but now I have another problem. Why is it saying this. I am just trying something out if it would work like this but it gives me this error but I dont know why

unknown.png
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I am doing it completely different, just found another way of doing it 😛

unknown.png
spring trench
gloomy lily
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And dont mind the Healtbar game object i just have it there since the begining for no reason. Thought I would need it at some point but I didnt

spring trench
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Add this Debug.Log to your first loop
on the Last Line

Debug.Log(gameObject.transform.Find($"Health Bar_Bar ({Lista})"))
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let me know what it says

gloomy lily
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It gives me objects from 1 to 31

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From 0, I just said from 1 because I have it named (1) first and so on

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But the first one is Null tho

spring trench
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Alright, good. You can remove the debug log.
Make a new one in the second loop:

Debug.Log(HealthBarList[i].GetComponent<Image>());
gloomy lily
spring trench
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Hm. Try moving the initialization of your list from the variable declaration, to the beginning of Start()

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By the way, if you need another script to access the list, then it should be public.
But since you don't need to expose the list to the inspector, you should add the attribute [HideInInspector]
or make the list private (only private, derp)

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[SerializeField] private or just public will expose the field to the inspector

gloomy lily
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Thats what you mean right?

unknown.png
gloomy lily
spring trench
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Not precisely. That would work for testing.
But you also made the list a local variable, which means you can't access it from outside the script, or other methods.
You can simply declare a list, and initialize it later:

private List<Transform> HealthBarList;

private void Start()
{
    HealthBarList = new List<Transform>();
}
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Between the loops, do this:

Debug.Log(HealthBarList.Count);
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Ah, I think I see the problem

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Game Objects in a Canvas have their Transform component swapped out by RectTransform
I believe your list either does not add any items, or it adds items with null values

Change the type of the list from Transform to RectTransform

gloomy lily
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you were indeed correct. Changed it from 0 to 1

unknown.png
spring trench
gloomy lily
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This one. I think I had 1 too many items

unknown.png
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Yeah silly me its 0 it starts with

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no wonder such a stupid mistake

spring trench
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ah, your Object NAMES start with 1

gloomy lily
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Thanks man, I appreciate sticking with me on this one I would spend ages figuring this out.

Yes before the underlined part was 0, which menas 31 items with 0 included, so now I just moved one number up and it started with 1. I have it on 0-30 right now to make it less confusing but yes the original problem was my stupid mistake of forgeting the list starts with 0 as a number and not 1

spring trench
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Tip: Only use < in the expression, not <= unless logic dictates it is required.
Stick to the standard, and you won't have to remember twice the amount of logic.
(from experience)

gloomy lily
spring trench
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right now it works, so don't break it again lol

gaunt comet
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this has been long. I've been out and around town, and its still on-going

gloomy lily
spring trench
gloomy lily
spring trench
spring trench
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I mean people who are outright non-friendly

gloomy lily
spring trench