includeOneToOne

gistfile1.js

    function includeOneToOne(callback) {
      var targetIds = [];
      var objTargetIdMap = {};

      var lookupKey = (relation.type === 'belongsTo') ? relation.keyFrom : relation.keyTo;

      for (var i = 0; i < objs.length; i++) {
        var obj = objs[i];
        if (relation.type === 'belongsTo') {
          if (obj[lookupKey] === null ||
            obj[lookupKey] === undefined) {
            defineCachedRelations(obj);
            obj.__cachedRelations[relationName] = null;
            continue;
          }
        }

        var targetId = obj[lookupKey];

        if (targetId) {
          targetIds.push(targetId);
          var targetIdStr = targetId.toString();
          objTargetIdMap[targetIdStr] = objTargetIdMap[targetIdStr] || [];
          objTargetIdMap[targetIdStr].push(obj);
        }
        defineCachedRelations(obj);
        obj.__cachedRelations[relationName] = null;
      }

      filter.where[lookupKey] = {
        inq: uniq(targetIds)
      };

      relation.applyScope(null, filter);

      findWithForeignKeysByPage(relation.modelTo, filter,
        lookupKey, 0, options, targetFetchHandler);

      /**
       * Process fetched related objects
       * @param err
       * @param {Array<Model>} targets
       * @returns {*}
       */
      function targetFetchHandler(err, targets) {
        if (err) {
          return callback(err);
        }
        var tasks = [];
        //simultaneously process subIncludes
        if (subInclude && targets) {
          tasks.push(function subIncludesTask(next) {
            relation.modelTo.include(targets, subInclude, options, next);
          });
        }
        //process each target object
        tasks.push(targetLinkingTask);
        function targetLinkingTask(next) {
          async.each(targets, linkOneToMany, next);
          function linkOneToMany(target, next) {
            var targetId = obj[lookupKey];
            var objList = objTargetIdMap[targetId.toString()];
            async.each(objList, function(obj, next) {
              if (!obj) return next();
              obj.__cachedRelations[relationName] = target;
              processTargetObj(obj, next);
            }, next);
          }
        }

        execTasksWithInterLeave(tasks, callback);
      }
    }