In repeater: validate that value is used once, and exactly once

[jjrohrer]

I have a personas repeater with one, or more persona in it. Each persona has a name, and slug. One, one only one, of the persona must have a slug set to 'guide'. Here is how I solved that validation (with help from examining ->distinct, and a bit of chatgpt 4o)

So, my form schema starts like this

And the validation looks like this:

   private static function ValidateOneAndExactlyOne_forGivenValueWithinRepeater(string $valueWeNeedOne_andExactlyOne_of, Closure $fail, Component $component, string $failureMessage): bool
    {

        // Get the parent repeater
        $repeater = $component->getParentRepeater();

        // Get the state path of the repeater
        $repeaterStatePath = $repeater->getStatePath();

        // Extract the component item state path relative to the repeater
        $componentItemStatePath = (string) str($component->getStatePath())
            ->after("{$repeaterStatePath}.")
            ->after('.');

        // Get the state of the repeater
        $repeaterState = $repeater->getState();

        // Get all the slugs in the repeater
        $slugs = Arr::pluck($repeaterState, $componentItemStatePath);

        // Count occurrences of the specific slug value
        $slugCount = collect($slugs)->countBy()->get($valueWeNeedOne_andExactlyOne_of, 0);

        // Validate that the value exists exactly once
        if ($slugCount !== 1) {
            $fail($failureMessage);
        }

        return true;

    }