js/libs/ember-data.js
function(record, array) {
    var loadingRecordArrays = record._loadingRecordArrays || [];
    loadingRecordArrays.push(array);
    record._loadingRecordArrays = loadingRecordArrays;
  }
function(record, array) {
    var loadingRecordArrays = record._loadingRecordArrays || [];
    loadingRecordArrays.push(array);
    record._loadingRecordArrays = loadingRecordArrays;
  }
Internally, we maintain a map of all unloaded IDs requested by a ManyArray. As the adapter loads data into the store, the store notifies any interested ManyArrays. When the ManyArray's total number of loading records drops to zero, it becomes `isLoaded` and fires a `didLoad` event.