Decrementing last string element in array without removing it in C#?

Question

I'm currently doing a demo on Unity where I've put the whole alphabet in an array. For the backspace function I want to decremt the last string element in the array, but it doesnt work.

[SerializeField] private GameObject keyboard;

[SerializeField] private Text keyboardInput;

private KeyCode[] MyKeys = {KeyCode.A, KeyCode.B,KeyCode.C,KeyCode.D, KeyCode.E,KeyCode.F,KeyCode.G,KeyCode.H,KeyCode.I,KeyCode.J,KeyCode.K,KeyCode.L,KeyCode.M,KeyCode.N,KeyCode.O,KeyCode.P,KeyCode.Q,KeyCode.R,KeyCode.S,KeyCode.T, KeyCode.U ,KeyCode.V,KeyCode.W,KeyCode.X,KeyCode.Y,KeyCode.Z, KeyCode.Space, KeyCode.Backspace };

private string[] currText;
void Start()
{
    keyboardInput.text = currText.ToString();
}

private void typeKeys()
{

    for (var i = 0; i < MyKeys.Length; i++)
    {

        if (Input.GetKeyDown(MyKeys[i]))
        {

            if (i == 0)
            {
                keyboardInput.text += "a";
            }
            else if (i == 1)
            {
                keyboardInput.text += "b";
            }
            else if (i == 2)
            {
                keyboardInput.text += "c";
            }
            else if (i == 3)
            {
                keyboardInput.text += "d";
            }
            else if (i == 4)
            {
                keyboardInput.text += "e";
            }
            else if (i == 5)
            {
                keyboardInput.text += "f";
            }
            else if (i == 6)
            {
                keyboardInput.text += "g";
            }
            else if (i == 7)
            {
                keyboardInput.text += "h";
            }
            else if (i == 8)
            {
                keyboardInput.text += "i";
            }
            else if (i == 9)
            {
                keyboardInput.text += "j";
            }
            else if (i == 10)
            {
                keyboardInput.text += "k";
            }
            else if (i == 11)
            {
                keyboardInput.text += "l";
            }
            else if (i == 12)
            {
                keyboardInput.text += "m";
            }
            else if (i == 13)
            {
                keyboardInput.text += "n";
            }
            else if (i == 14)
            {
                keyboardInput.text += "o";
            }
            else if (i == 15)
            {
                keyboardInput.text += "p";
            }
            else if (i == 16)
            {
                keyboardInput.text += "q";
            }
            else if (i == 17)
            {
                keyboardInput.text += "r";
            }
            else if (i == 18)
            {
                keyboardInput.text += "s";
            }
            else if (i == 19)
            {
                keyboardInput.text += "t";
            }
            else if (i == 20)
            {
                keyboardInput.text += "u";
            }
            else if (i == 21)
            {
                keyboardInput.text += "v";
            }
            else if (i == 22)
            {
                keyboardInput.text += "w";
            }
            else if (i == 23)
            {
                keyboardInput.text += "x";
            }
            else if (i == 24)
            {
                keyboardInput.text += "y";
            }
            else if (i == 25)
            {
                keyboardInput.text += "z";
            }
            else if (i == 26)
            {
                keyboardInput.text += " ";
            }
            else if (i == 27)
            {
                currText = currText.Take(currText.Length - 1).ToArray();
            }
        }
    };
}

// Update is called once per frame
void Update()
{

    typeKeys();
}

This is the part im trying to get to work

                else if (i == 27)
            {
                currText = currText.Take(currText.Length - 1).ToArray();
            }

See video for clarification

What I mean by that it doesnt work is that I cant remove the last letter from my array thus giving the effect of using backspace in a sentence in my virtual setup. This is the whole script.

All i see from your code is you are always adding to your "keyboardInput" variable. In which point are you adding to your "currText" variable ? From your code i can say it is always an empty string. — Çağatay IŞIK
– Çağatay IŞIK, Commented Nov 30, 2020 at 21:55

Milan Egon Votrubec · Accepted Answer · 2020-12-01 03:49:05Z

3

Let's start by reducing the amount of code. And then, after that, we can also take advantage of two facts; Unity has a KeyCode enum, and the alphabet is ordered in values from 'a' through to 'a'+25. I'll clarify that with a bit of code:

private Text keyboardInput;
List<char> charList = new List<char> ( );

private void typeKeys( )
{
    var length = charList.Count;

    if ( Input.GetKeyDown ( KeyCode.Space ) )
        charList.Add ( ' ' );

    if ( Input.GetKeyDown ( KeyCode.Backspace ) && length  > 0 )
        charList.RemoveAt ( length - 1 );

    for ( var i = 0; i < 26; i++ )
        if ( Input.GetKeyDown ( KeyCode.A + i ) ) charList.Add ( ( char ) ( 'a' + i ) );

    if ( length != charList.Count ) keyboardInput.text =  string.Concat ( charList );
}

What I'm doing here, is first checking for the Space key, followed by the Backspace key. After that, I iterate through the alphabet characters, adding the i value to the KeyCode.A. Remember that enums are just int by default. If that's a match, we add the corresponding i value to the 'a' character and add that to the List<char> list, remembering to also cast the resulting value back to a char first.

Finally, if the length of your character array has changed, then, and only then, do we update your keyboardInput.text. That's to help save string garbage being produced every single frame. We can Concat a char IEnumerable to a string.

Using this method you can remove the whole line that starts with private KeyCode[] MyKeys. You don't need to store all of the KeyCode values in an array to check against.

edited Dec 1, 2020 at 3:49

answered Nov 30, 2020 at 23:13

Milan Egon Votrubec

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1 Comment

Kemura Over a year ago

Wow! What a great Solution! I'm fairly new to C# so I have no prior experience with enums or the List system. I'm used to only working within the spectrum of arrays but this was an eye opener :). Thank you for your help! There is still a lot to be done since I'm trying to implement det å, ä, ö keys (this demo is based on a swedish keyboard) but this was a great start. Thanks again!

Enigmativity · Accepted Answer · 2020-12-01 02:39:19Z

0

This isn't an answer to your question, and to get a proper answer you'll need to post your complete code and a good explanation of what's going wrong, but I thought I'd post this as it might be useful to you.

I've refactored you typeKeys() method.

private void typeKeys()
{
    foreach (var key in MyKeys.Where(k => k != KeyCode.Space).Where(k => k != KeyCode.Backspace))
    {
        if (Input.GetKeyDown(key))
        {
            keyboardInput.text += key.ToString().ToLower();
        }
    }
    if (Input.GetKeyDown(KeyCode.Space))
    {
        keyboardInput.text += " ";
    }
    if (Input.GetKeyDown(KeyCode.Backspace))
    {
        currText = currText.Take(currText.Length - 1).ToArray();
    }
}

That's it.

The line currText = currText.Take(currText.Length - 1).ToArray(); should work to truncate a properly defined array by one element or simply keep it at zero elements.

edited Dec 1, 2020 at 2:39

answered Nov 30, 2020 at 21:58

Enigmativity

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1 Comment

Ruzihm Over a year ago

Way more readable. I do think it needs a condition in the if (Input.GetKeyDown(key)) block to handle the case where k == KeyCode.Space

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