Method add

lib/associations/belongs-to-many.js:672–753

* Associate one or several rows with source instance. It will not un-associate any already associated instance * that may be missing from `newInstances`. * * @param {Model} sourceInstance source instance to associate new instances with * @param {Model|Model[]|string[]|string|number[]|num

(sourceInstance, newInstances, options)

   * @returns {Promise}
   */
  async add(sourceInstance, newInstances, options) {
    // If newInstances is null or undefined, no-op
    if (!newInstances) return Promise.resolve();

    options = { ...options };

    const association = this;
    const sourceKey = association.sourceKey;
    const targetKey = association.targetKey;
    const identifier = association.identifier;
    const foreignIdentifier = association.foreignIdentifier;
    const defaultAttributes = options.through || {};

    newInstances = association.toInstanceArray(newInstances);

    const where = {
      [identifier]: sourceInstance.get(sourceKey),
      [foreignIdentifier]: newInstances.map(newInstance => newInstance.get(targetKey)),
      ...association.through.scope
    };

    const updateAssociations = currentRows => {
      const promises = [];
      const unassociatedObjects = [];
      const changedAssociations = [];
      for (const obj of newInstances) {
        const existingAssociation = currentRows && currentRows.find(current => current[foreignIdentifier] === obj.get(targetKey));

        if (!existingAssociation) {
          unassociatedObjects.push(obj);
        } else {
          const throughAttributes = obj[association.through.model.name];
          const attributes = { ...defaultAttributes, ...throughAttributes };

          if (Object.keys(attributes).some(attribute => attributes[attribute] !== existingAssociation[attribute])) {
            changedAssociations.push(obj);
          }
        }
      }

      if (unassociatedObjects.length > 0) {
        const bulk = unassociatedObjects.map(unassociatedObject => {
          const throughAttributes = unassociatedObject[association.through.model.name];
          const attributes = { ...defaultAttributes, ...throughAttributes };

          attributes[identifier] = sourceInstance.get(sourceKey);
          attributes[foreignIdentifier] = unassociatedObject.get(targetKey);

          Object.assign(attributes, association.through.scope);

          return attributes;
        });

        promises.push(association.through.model.bulkCreate(bulk, { validate: true, ...options }));
      }

      for (const assoc of changedAssociations) {
        let throughAttributes = assoc[association.through.model.name];