C#•3y ago

❔ Adding to Arrays Via Methods

I am having trouble getting arrays to be changed by methods. I tried lists as well. Please send help.

82 Replies

Angius•3y ago

You can't append items to arrays They're fixed-size Use a List<T>

string[] plants = {};

createPlant(ref plants);
createPlant(ref plants);
createPlant(ref plants);
Console.WriteLine(plants[0] + plants[1]);
Console.ReadLine();
// avolva aventine  
static void createPlant(ref string[] plants)
{
    Console.WriteLine("What is the Name of your Plant?");
    plants = new string[] { Console.ReadLine() };
    Console.Write("Completed! Push any Button to Exit.");
    Console.ReadLine();
    //may just have to for now.
    string print = ""; 
    for (int i = 0; i < plants.Length; i++) 
    {
        Console.Write(plants[i] + ", ");
    }
    Console.WriteLine(print);
    Console.ReadLine();
}

string[] plants = {};

createPlant(ref plants);
createPlant(ref plants);
createPlant(ref plants);
Console.WriteLine(plants[0] + plants[1]);
Console.ReadLine();
// avolva aventine  
static void createPlant(ref string[] plants)
{
    Console.WriteLine("What is the Name of your Plant?");
    plants = new string[] { Console.ReadLine() };
    Console.Write("Completed! Push any Button to Exit.");
    Console.ReadLine();
    //may just have to for now.
    string print = ""; 
    for (int i = 0; i < plants.Length; i++) 
    {
        Console.Write(plants[i] + ", ");
    }
    Console.WriteLine(print);
    Console.ReadLine();
}

@Angius thanks but look at this

HumNumWorldOP•3y ago

HumNumWorldOP•3y ago

its error after error

Angius•3y ago

The parameter is declared as a string[], so obviously it won't take a List<string> Also, in your CreatePlant() method you crate a brand new array You don't add anything, you replace

HumNumWorldOP•3y ago

can you explain that

Angius•3y ago

What's to explain there? Square peg doesn't fit into a round hole int and string are different types So are boolean and UngaBunga

HumNumWorldOP•3y ago

where is the square peg

Angius•3y ago

So are string[] and List<string> List<string> is the square peg The method has a round hole, string[] type parameter List<T> is not T[]

HumNumWorldOP•3y ago

oh ignore the writeline

Angius•3y ago

Nothing to do with any writeline

HumNumWorldOP•3y ago

HumNumWorldOP•3y ago

right here where is the []

HumNumWorldOP•3y ago

HumNumWorldOP•3y ago

and ignore line 27 for now im just trying to get the errors off the first part until it functions

Angius•3y ago

Aight, so, why do you try to pass ref List<string> plants as a parameter? Do you also use Console.WriteLine(string "message")?

HumNumWorldOP•3y ago

apparently to change a variable in a function you have to use ref I tried just "plants" but it said it has to be written like a list

Angius•3y ago

Yeah, in the parameter declaration

HumNumWorldOP•3y ago

was there a better way of doing that

Angius•3y ago

When you call the method, you don't supply a type You just pass the param

HumNumWorldOP•3y ago

wym

Angius•3y ago

CreatePlant(plants)

HumNumWorldOP•3y ago

like this?

Angius•3y ago

Not here Jesus $helloworld

MODiX•3y ago

Written interactive course https://learn.microsoft.com/en-us/users/dotnet/collections/yz26f8y64n7k07 Videos https://dotnet.microsoft.com/learn/videos

HumNumWorldOP•3y ago

im used to javascript

Angius•3y ago

You really should brush up the basics

HumNumWorldOP•3y ago

its much easier when I could do something like: appendItem("plants", ""); which I dont even know if thats a real thing

Angius•3y ago

And you can

HumNumWorldOP•3y ago

because I learned from code.org

Angius•3y ago

var plants = new List<string>();
plants.Add("carrot");
plants.Add("hydrangea");
plants.Add("juniper");

var plants = new List<string>();
plants.Add("carrot");
plants.Add("hydrangea");
plants.Add("juniper");

List has the .Add() method

HumNumWorldOP•3y ago

yeah see I get that but I called plants in main and im trying to add in a method and its causing tons of errors to get it through the parameters like in js, everything is global pretty much I just say:

var x = 1

function addOne() {
x ++;
}

var x = 1

function addOne() {
x ++;
}

and var becomes 2 if I call the function in c# i'm just lost with methods and why they are so isolated you have to use ref for some reason for it to change anything, and even still its like a maze to get the errors to be broken

Angius•3y ago

Angius•3y ago

For reference types, you don't need to use ref

HumNumWorldOP•3y ago

List<string> plants = new List<string>();
createPlant(ref List<string> plants);
Console.ReadLine();

static void createPlant(plants)
{
    Console.WriteLine("What is the Name of your Plant?");
    plants.Add(Console.ReadLine());
    Console.Write("Completed! Push any Button to Exit.");
    Console.ReadLine();
    //may just have to for now.
    string print = ""; 
    for (int i = 0; i < plants.Length; i++) 
    {
        Console.Write(plants[i] + ", ");
    }
    Console.WriteLine(print);
    Console.ReadLine();
}

List<string> plants = new List<string>();
createPlant(ref List<string> plants);
Console.ReadLine();

static void createPlant(plants)
{
    Console.WriteLine("What is the Name of your Plant?");
    plants.Add(Console.ReadLine());
    Console.Write("Completed! Push any Button to Exit.");
    Console.ReadLine();
    //may just have to for now.
    string print = ""; 
    for (int i = 0; i < plants.Length; i++) 
    {
        Console.Write(plants[i] + ", ");
    }
    Console.WriteLine(print);
    Console.ReadLine();
}

oh let me read this rq

Angius•3y ago

And here's the fix to your issue You declare types when declaring the method There and only ever there When calling that method, you don't declare any types Just pass the params

HumNumWorldOP•3y ago

Angius•3y ago

Cool, what does the error say

HumNumWorldOP•3y ago

argument 1 must be passed with the 'ref' keyword

Angius•3y ago

Well, try that

HumNumWorldOP•3y ago

oh wow ok brb ok yeah its cleared up next issue though

HumNumWorldOP•3y ago

Angius•3y ago

Again, what does the error say? probably says that .Length property doesn't exist on List<T>

HumNumWorldOP•3y ago

Angius•3y ago

That's because those are the properties List<T> has: https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.list-1?view=net-7.0#properties .Length is not among them .Count, however, is

HumNumWorldOP•3y ago

are there any substitutes ah thats weird i'll try it oh wow thats wonderful it works ok now I need a few clarifications so I really grasp this this is whats confusing me its the whole parameters and redeclarations thing

Angius•3y ago

The method declares what it wants

void Foo(string x, int y) {}

void Foo(string x, int y) {}

like this one, that wants a string and an int When calling that method, you don't need to say that you're passing a string

HumNumWorldOP•3y ago

hold up

Angius•3y ago

No need to do

string x = "hello";
Foo(string x, int 69);

string x = "hello";
Foo(string x, int 69);

because the method will not let you pass anything else. You just do

string x = "hello";
Foo(x, 69);

string x = "hello";
Foo(x, 69);

HumNumWorldOP•3y ago

wow so ref only needs to be sent in the declaration of the method

Angius•3y ago

Admittedly, I haven't really worked with ref

HumNumWorldOP•3y ago

it seems so obvious, swapping syntaxes really gets me a headache

Angius•3y ago

To begin with, List<T> already is a reference type

HumNumWorldOP•3y ago

a what?

Angius•3y ago

You're already passing a reference to it, not a copy $refvsvalue

MODiX•3y ago

https://cdn.discordapp.com/attachments/364492811489509376/692833980650881084/pass-by-reference-vs-pass-by-value-animation.gif

Angius•3y ago

In C# there are value types — mostly the basic ones like int, bool, etc And reference types — custom classes and stuff Value types, when passed, create a copy Reference types pass a reference

HumNumWorldOP•3y ago

oh so I only use ref when I need to make the copy change something outside

MODiX•3y ago

Angius#1586

REPL Result: Success

var list = new List<int> { 1, 2, 3 };

static void AddNumber(List<int> l)
{
    l.Add(Random.Shared.Next(0, 100));
}

AddNumber(list);
AddNumber(list);
AddNumber(list);

list

var list = new List<int> { 1, 2, 3 };

static void AddNumber(List<int> l)
{
    l.Add(Random.Shared.Next(0, 100));
}

AddNumber(list);
AddNumber(list);
AddNumber(list);

list

Result: List<int>

Compile: 606.838ms | Execution: 36.419ms | React with ❌ to remove this embed.

Angius•3y ago

ref coerces value types to be passed as reference

HumNumWorldOP•3y ago

wait so saying a variable prints it? I see you wrote list

Angius•3y ago

That list without a semicolon is just something the repl of the bot does

HumNumWorldOP•3y ago

ah I had trouble earlier with printing arrays

MODiX•3y ago

Angius#1586

REPL Result: Success

int x = 96;

void Foo(int num) {
    num = 420;
    Console.WriteLine($"num is {num}");
}
Foo(x);
Console.WriteLine(x);

void Bar(ref int num) {
    num = 420;
    Console.WriteLine($"num is {num}");
}
Bar(ref x);
Console.WriteLine(x);

int x = 96;

void Foo(int num) {
    num = 420;
    Console.WriteLine($"num is {num}");
}
Foo(x);
Console.WriteLine(x);

void Bar(ref int num) {
    num = 420;
    Console.WriteLine($"num is {num}");
}
Bar(ref x);
Console.WriteLine(x);

Console Output

num is 420
96
num is 420
420

num is 420
96
num is 420
420

Compile: 681.702ms | Execution: 78.655ms | React with ❌ to remove this embed.

Angius•3y ago

Here's how ref works for value types Without ref, the change happened inside of the method, the copy of the number was changed With ref, the change happened inside and outside of the method

HumNumWorldOP•3y ago

Sorry my network is acting up. So I get it now! reference = ref. if I did val to a ref then would it act like a value?

Angius•3y ago

No You can pass a value type as a reference, but you can't turn a reference type into a value type

HumNumWorldOP•3y ago

hm and I know this is off topic but what do you do for the " cannot implicitly convert type 'string' to 'int' " error

Angius•3y ago

int.Parse() for example Or better yet, int.TryParse() But this one's a little more complex

HumNumWorldOP•3y ago

what what do those mean

MODiX•3y ago

Angius#1586

REPL Result: Success

string str = "69";
int num = int.Parse(str);
num

string str = "69";
int num = int.Parse(str);
num

Result: int

Compile: 475.533ms | Execution: 31.322ms | React with ❌ to remove this embed.

HumNumWorldOP•3y ago

what does the word parse mean

Angius•3y ago

It's the name of the method...? Like Console.WriteLine()

HumNumWorldOP•3y ago

I'm guessing over all it converts

Angius•3y ago

It parses a string into a number, yeah You could say converts, sure

HumNumWorldOP•3y ago

and one last question how do you close the program through code

Angius•3y ago

Once it completes, it'll just close IIRC you can just return from it as well

HumNumWorldOP•3y ago

ah ty thats everything, thank you for your help!

Angius•3y ago

Anytime

Accord•3y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Adding to Arrays Via Methods

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