settings.js

const Gio = imports.gi.Gio;
const ExtensionUtils = imports.misc.extensionUtils;
const Extension = ExtensionUtils.getCurrentExtension();

//const SCHEMA_PATH = 'org.gnome.shell.extensions.com.eimji.setproxies';

function getSettings(schema) {
    let extension = ExtensionUtils.getCurrentExtension();

    schema = schema || extension.metadata['settings-schema'];

    const GioSSS = Gio.SettingsSchemaSource;

    let schemaDir = extension.dir.get_child('schemas');
    let schemaSource;
    if (schemaDir.query_exists(null))
        schemaSource = GioSSS.new_from_directory(schemaDir.get_path(),
            GioSSS.get_default(),
            false);
    else
        schemaSource = GioSSS.get_default();

    let schemaObj = schemaSource.lookup(schema, true);
    if (!schemaObj)
        throw new Error('Schema ' + schema + ' could not be found for extension ' + extension.metadata.uuid);

    return new Gio.Settings({ settings_schema: schemaObj });
};