Using withDocument HOC to refer to the document in a preview component

export default {
    name: 'parentObject',
    title: 'Parent',
    type: 'document',
    fields: [
        {
            name: 'showCorrectness',
            title: 'Show Correctness',
            type: 'boolean',
        },
        {
            name: 'answers',
            title: 'Answers',
            type: 'array',
            of: [{ type: 'childObject' }],
        },
    ],
};

import React from 'react';

export default {
    name: 'childObject',
    title: 'Child Object',
    type: 'object',
    fields: [
        {
            title: 'Text',
            name: 'text',
            type: 'string',
        },
        {
            title: 'Is correct',
            name: 'isCorrect',
            type: 'boolean',
            hidden: ({ document }) => {
                return !document.showCorrectness;
            },
            validation: (Rule) =>
                Rule.custom((correctness, { document }) => {
                    if (!document.showCorrectness) {
                        return true;
                    }

                    return 'Correctness required';
                }),
        },
    ],
    preview: {
        select: {
            isCorrect: 'isCorrect',
            text: 'text',
        },
        prepare(child) {
            const PARENT_ICON = {
                correct: '✅',
                incorrect: '❌',
                neutral: '🔵',
            };

            let parentIcon = PARENT_ICON.neutral;

            if (document.showCorrectness) {
                parentIcon = child.isCorrect ? PARENT_ICON.correct : PARENT_ICON.incorrect;
            }

            return {
                title: child.text,
                media: <p>{parentIcon}</p>,
            };
        },
    },
};