paging.js

class AttachmentActions {
  readPage(pageRecord) {
    return AttachmentAPI.readPage(pageRecord)
        .then(stuff => this.actions.readPageSuccess(stuff, pageRecord));
  }
}

class AttachmentStore {
  fetchNextPage() {
    let pageRecord = this.getNextPageRecord();
    let stuff = this.getStuffFromCache(pageRecord); // how do you maintain this?

    if (hasInCache) {
      return Promise.resolve(stuffFromCache);
    }
    
    return AttachmentActions.readPage(pageRecord)
        .then(() => this.getStuffFromCache());
  }
}