Using It

This page will guide you through an example, highlighting the unique aspects of Itergia Core.

Writing JavaScript Mutator Code

The mutators are JavaScript functions running inside a transaction. They are stateless, and interact only through its two arguments:

intent contains the parameters and authorization information.
system is an interface to manipulate the schema's objects.

Here, we create a helper function called queryListByID, to reduce repetition.

export async function createList(intent, system) {
  const id = intent.generateIDBytes("list");
  if (await queryListByID(system, id)) {
    throw new Error(`duplicate list ID: ${id}`);
  }

  await system.create("List", {
    ...intent.fields,
    id,
  });
}

export async function addItem(intent, system) {
  const list = await queryListByID(
    system,
    intent.fields.listId);
  if (!list) {
    throw new Error(
      `unknown list: ${intent.fields.listId}`);
  }

  intent.fields.prototype.id =
    intent.generateIDBytes('item');
  list.fields.items.push(intent.fields.prototype);

  await list.update(list.fields);
}

// Other mutator functions left out.

async function queryListByID(system, id) {
  const query = system.query
    .from("List")
    .filter("fields.id == bytes(_0)",
      {
        args: [id],
      });
  return await query.asSingletonOr(undefined);
}

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