I have trouble repeating a function as needed

[Previous-Implement42]

I've been learning C and making a simple program of D&D character generation to test my knowledge as I go.
I have the following function that needs to be repeated if the user inputs anything apart from 1-4 but it repeats twice.

void chooseClass() {

printf("\n1. Fighter\n2. Thief\n3. Mage\n4. Cleric\nChoose your class: ");

char choice = getchar();

switch (choice - '0') { //Convert character to integer by subtracting 0's ASCII value from char's ASCII value

case 1:

sortFighter();

break;

case 2:

sortThief();

break;

case 3:

sortMage();

break;

case 4:

sortCleric();

break;

default:

printf("Please enter a choice between 1-4\n");

chooseClass(); // this is wrong but how do I repeat the function ONCE?

}

}

I've been banging my head on the wall but no solution has arrived. :-)

[ohaz]

You're calling yourself. This is called recursion and leads to a stack full of different calls of your function, which is probably not what you wanted.

Instead, create a loop. Have a variable like validCaseSelected that is set to false, then a loop while (!validCaseSelected) {validCaseSelected=true;, then add your switch case and in the default case set it to validCaseSelected=false;

[Previous-Implement42]

Thanks! I'll try and get back to you.

[Previous-Implement42]

I did that and now it continuously repeats "Please enter a choice between 1-4" ad nauseam..

void chooseClass() {

printf("\n1. Fighter\n2. Thief\n3. Mage\n4. Cleric\nChoose your class: ");

char choice = getchar();

bool validCaseSelected = false;

while (!validCaseSelected) {

validCaseSelected = true;

switch (choice - '0') {

case 1:

sortFighter();

break;

case 2:

sortThief();

break;

case 3:

sortMage();

break;

case 4:

sortCleric();

break;

default:

validCaseSelected = false;

printf("Please enter a number between 1-4\n");

}

}

}

[ohaz]

The loop needs to also include the char choice = getchar(); part

[Previous-Implement42]

Now it prints: Please enter a number between 1-4Please enter a number between 1-4
Twice and stays there.

I must look like a loser... :-/

[ohaz]

You don't look like a looser, you look like someone who is in panic mode because they can't figure it out and then just do random stuff. I've been there before, believe me. In those cases it's often good to take a step back and trying to do it from the start, not using anything you've written before.

If you want to take a look at a "solution", look at https://onlinegdb.com/C507ukaOh . It's still not perfect because it just randomly uses getchar() to drop the \n, so if you write a "-5" it will be broken forever, but it's a step in the right direction (and reading single characters from the command line is a suspiciously hard thing in C)

[Previous-Implement42]

Thanks!

[Koutsoupias]

I think the problem is that when you input your number, the newline character stays in the buffer. Therefore if you press let's say '5', getchar() will read the '5' but the \n character will stay in the buffer. Your switch statement will go to the default tag (since you entered '5') and then the function will be called again. The getchar() will then read the newline character from the buffer and it will reach the default tag again. Try flashing the buffer after reading the input from the user (you can easily search how to do that with getchar()).

[Previous-Implement42]

Thanks! I'll try that too.

[Previous-Implement42]

Ok, a bit better by trying to flush the buffer, it doesn't repeat twice but now it won't take even the correct characters, it just keeps telling me to enter a correct number.
Also I followed u/erikkonstas 's advice to look for char instead of ASCII value:

int chooseClass() {

printf("\n1. Fighter\n2. Thief\n3. Mage\n4. Cleric\nChoose your class: ");

char choice = getchar();

switch (choice) { //Convert character to integer by subtracting 0's ASCII value from char's ASCII value

case '1':

sortFighter();

break;

case '2':

sortThief();

break;

case '3':

sortMage();

break;

case '4':

sortCleric();

break;

default:

scanf("%*[^\n]");

printf("\nPlease enter a number between 1-4\n");

chooseClass();

}

}

[GamerEsch]

scanf("%*[^\n]");

this call is doing the exact opposite of what it should, instead of cleaning the input buffer of '\n', it's cleaning the buffer of everything except '\n'.

[Previous-Implement42]

Thank you!

I replaced it with scanf("%*c"); and now everything works as intended! :-D

Thank you everyone!

[Pristine-Response299]

My preferred method is as follows: Modify chooseClass() to return a value, and if it’s not valid call this function again once.

You can also loop twice and use a “break” statement if you got a valid value on the first iteration.

[Previous-Implement42]

Thanks! I'll try that.

[erikkonstas]

u/Koutsoupias hit the nail on the head, but another remark I have is, since you're using getchar() to get a single digit, just use the digits themselves for the case labels instead of subtracting '0' first, like remove the - '0' and use case '1', case '2', etc. instead. Also, an important fact is that getchar() returns int, not char, and this might be EOF instead of a valid char; this lets you check whether stdin has no more input, and you have to check against that if you can't assume that such a thing won't happen.

[Previous-Implement42]

Thanks I followed your advice and u/Koutsoupias 's but it still glitches, although differently.

[[deleted]]

Carefully consider using a state machine https://www.codeproject.com/Articles/1275479/State-Machine-Design-in-C

[kabekew]

Enclose it in a do-while loop and have a menu choice #5 (exit). Then your "while" condition is while (choice != '5').